THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 

LOS  ANGELES 

GIFT  OF 

John  S.Prell 


/, 


REFRIGERATION 


A  PRACTICAL  TREATISE  ON  THE  PRODUCTION  OF  LOW 
TEMPERATURES    AS    APPLIED    TO    THE    MANU- 
FACTURE OF  ICE  AND  TO  THE  DESIGN 
AND   OPERATION  OF  COLD 
STORAGE  PLANTS 


By  MILTON  W.  ARROWOOD 

GRADUATE,  UNITED  STATES  NAVAL  ACADEMY 

REFRIGERATING    AND    MECHANICAL    ENGINEER 

WITH  THE  TRIUMPH  ICE  MACHINE  CO. 

JOHfU  S.  PRELL 

Gvil  6*  Mechanical  Engineer. 

SAN  FRANCISCO,  CAL. 

ILLUSTRATED 


CHICAGO 

AMERICAN  SCHOOL  OF  CORRESPONDENCE 
1913 


COPYRIGHT,  1913,  BY 
AMERICAN  SCHOOL  OF  CORRESPONDENCE 


COPYRIGHTED  IN  GREAT  BRITAIN 
ALL,  RIGHTS  RESERVED 


Civil  &  Mechanical  Engineer. 

A  In 

A/ 


PAGE 

Historical 1 

Air  machine 2 

Definitions 3 

Heat 4 

Units  of  heat  measurement 6 

Unit  of  plant  capacity 13 

Radiation 18 

Convection 19 

Conduction 20 

Production  of  cold 20 

Tests  of  refrigerants 33 

Systems  of  refrigeration 36 

Cold-air  machine 36 

Arrangement  of  air  system 37 

Commercial  form  of  air  machine 38 

Compressor  cylinder 41 

Vacuum  process 44 

Vacuum  pump 45 

Absorption  system 46 

Generator 48 

Analyzer 48 

Condenser 50 

Rectifier 50 

Equalizer 50 

Absorber 51 

Ammonia  pump 52 

Ammonia  regulator 53 

Operation 53 

Power  for  absorption  plant : 53 

Binary  systems 56 

Care  and  management ' 57 

Charging 7374O1 5° 

.^ns-.i.e-ilAiE. 

LflM»ry 


2  CONTENTS 

Absorption  system  p  AGE 

Efficiency  tests 60 

Economy  of  absorption  machine 61 

Compression  system 61 

Operating  principle 62 

Compressors 64 

Essentials  in  compressors 66 

Compressor  valves 67 

Valve  operation 71 

Valve  proportions 72 

Compressor  piston 73 

Stuffing  box 75 

Water  jacket 76 

Lubrication 78 

Commercial  machines 81 

Horizontal  double-acting 81 

Vertical  compressors 85 

Carbon  dioxide  machines 87 

Small  refrigerating  plants 90 

Compressor  losses 93 

Ammonia  condensers 94 

Submerged  condenser 95 

Atmospheric  condenser 98 

Double-pipe  condenser.  . . 104 

Oil  separator  or  interceptor 109 

Cooling  towers 109 

Evaporators 113 

Brine  tank 114 

Brine  cooler 118 

Auxiliary  apparatus 125 

Ammonia  receiver 125 

Pipes 125 

Valves : 128 

Pressure  gauges 128 

Methods  of  refrigeration 131 

Proportion  between  parts  of  refrigerating  plant 132 

Testing  and  charging 134 


CONTENTS  3 

FACE 

Operation  and  management  of  plant 140 

Loss  of  ammonia 142 

Purging  and  pumping  out  connection 143 

Ice-making  plants 145 

Can  system 146 

Can  plant  equipment 147 

Distilling  apparatus 148 

Steam  condenser 149 

Hot  skimmer  and  rcboiler 149 

Filters 152 

Cooling  coils  and  gas  cooler .  152 

Freezing  tank 154 

Expansion  coils 154 

Ice  cans 155 

Grating  and  covers 156 

Brine  agitators 156 

Crane  and  hoist.' 158 

Dumping  and  filling 158 

Layout 160 

Plate  system 162 

Storing  and  selling  ice 174 

Ice-plant  insulation 176 

Tank  insulation 177 

General  cold  storage 178 

Conditions  for  preservation 179 

Insulation 182 

Non-conductors 183 

Methods  of  cooling 191 

Refrigeration  required 197 

Cold  storage 198 

Handling  goods 198 

Storage  rates 201 

Applications  of  refrigeration 202 

Breweries 202 

Packing  houses 202 

Creameries 203 

Miscellaneous  applications.  . .- 204. 


INTRODUCTION 

rT"'HE  production  of  low  temperatures  by  artificial  means  is 
centuries  old  and  even  the  methods  involving  the  use  of  lique- 
fied gases  have  been  known  since  1850.  It  is  only  in  the  last  few 
years,  however,  that  cold  storage  methods  have^been  extensively 
applied,  and  very  few  of  us  stop  to  realize  the  influence  which  this 
means  of  preserving  our  meats,  fish,  poultry,  vegetables,  etc.,  has 
had  upon  the  marketing  of  our  perishable  produce.  Perhaps  we 
sometimes  feel  that  the  cold  storage  companies  often  make  an 
unfair  use  of  their  powers  of  control  in  order  to  manipulate  prices 
but  certainly  in  the  end  the  results  make  for  the  general  welfare 
of  the  public. 

<I  The  most  efficient  and  probably  the  most  widely  used  method 
of  producing  lowjtemperatures — the  ammonia  process — is  exten- 
sively used  in  the  manufacture  of  artificial  ice.  This  has  become 
an  exceedingly  important  industry,  particularly  in  climates  where 
no  natural  ice  is  possible  except  by  a  long  freight  haul.  Both  the 
can  and  the  plate  systems  are  carefully  treated  and  minute  details 
in  regard  to  design  and  operation  of  a  plant  are  given. 
<J  The  author  has  treated  the  subject  from  a  practical  rather  than 
a  theoretical  standpoint,  giving  only  enough  physical  theory  on 
the  problems  of  heat  measurement,  pressure,  and  temperature 
to  make  the  text  understandable.  The  fact  that  the  material  was 
written  for  the  correspondence  courses  of  the  American  School  is 
sufficient  proof  of  its  clearness  and  practical  character,  and  it  is 
the  hope  of  the  publishers  that  the  book  will  be  of  interest  to  a 
wide  circle  of  readers. 


REFRIGERATION 

PART  I 


Historical.  Just  as,  in  the  realm  of  applied  electricity,  progress 
has  been  made,  not  by  accidental  discoveries  and  fortunate  inven- 
tions, but  by  careful  study  and  application  of  principles  learned  in 
scientific  research,  so  refrigeration  is  produced  mechanically  with 
apparatus  designed  and  perfected  by  applying  known  principles. 
The  history  of  the  refrigerating  machine  is  a  history  of  steady  growth 
and  development.  As  knowledge  of  physical  and  chemical  laws 
has  become  more  extensive,  particularly  as  related  to  the  action  of 
gases  and  heat  transfers,  the  refrigerating  machine  has  been  im- 
proved, until  to-day  it  is  able  to  make  ice  that  can  be  sold  in  com- 
petition with  the  product  of  Nature's  factory.  History  shows  that 
ice  was  used  for  domestic  purposes  as  early  as  the  time  of  Nero,  this 
monarch  having  had  ice  houses  built  in  Rome  for  storing  natural  ice. 
Moreover,  it  is  believed  that  the  ancients  had  knowledge  of  means 
to  produce  refrigeration  by  artificial  processes,  as  by  the  evaporation 
of  water  or  other  liquid  in  strong  air-currents.  Also,  they  are  thought 
to  have  used  freezing  mixtures  of  various  kinds,  one  of  the  most 
common  being  that  of  salt  and  ice,  as  used  by  every  housekeeper  of 
to-day  in  making  frozen  creams. 

When  one  considers  that  all  refrigeration  is  produced  by  the 
evaporation  of  certain  liquids,  it  is  seen  at  once  that  the  ancients  used 
the  right  principles,  whether  or  not  their  history — if  it  could  be  better 
known  to-day — would  show  that  they  had  mechanical  genius  and 
inventive  capacity  sufficient  to  develop  a  practical  machine  for  pro- 
ducing refrigeration  mechanically.  Antiquarian  researches  have 
shown  that  in  certain  particulars  the  mechanical  genius  of  the  an- 
cients was  greater  than  that  of  our  own  day;  and  we  may  well  wonder 
whether  or  not  they  were  able  to  develop  a  successful  refrigerating 
machine.  Whatever  knowledge  the  ancients  may  have  possessed 


2  i       REFRIGERATION 

along  these  lines,  was  lost  in  the  various  upheavals  that  convulsed 
the  world  down  to  the  end  of  the  Dark  Ages,  at  which  time  modern 
history  begins.  Records  since  that  time  show  that  the  cooling  effect 
obtained  by  dissolving  certain  salts  was  recognized  as  a  process  some 
three  hundred  years  ago,  the  method  having  first  been  used  about 
1607,  and  later,  1762,  by  Fahrenheit. 

Mechanical  apparatus  for  producing  cold  dates  from  a  much 
more  recent  period,  the  first  authentic  record  of  any  such  invention 
being  the  machine  of  Dr.  Cullen  for  evaporating  water  under  a 
vacuum.  This  machine  was  put  in  operation  about  1755.  About 
this  time,  also,  experiments  were  made  in  France  by  Lavoisier,  for 
using  ether  in  refrigerating  machines;  but  little  or  nothing  came  of 
either  of  these  men's  efforts,  and  it  was  not  until  the  early  part  of  the 
nineteenth  century  that  refrigeration  by  mechanical  means  began  to 
assume  a  practical  form.  About  1810,  Leslie  experimented  with  a 
machine  using  sulphuric  acid  and  water;  and  in  1824  a  machine  was 
patented  by  Vallance,  in  which  dry  air  was  circulated  over  shallow 
trays  of  water,  the  resulting  evaporation  abstracting  a  large  amount 
of  heat;  this  latter  process  for  cooling  water  was  used  in  India  from 
a  time  prior  to  the  dawn  of  modern  history. 

From  the  beginning  of  the  nineteenth  century  on,  the  develop- 
ment of  the  refrigerating  machine  was  rapid  and  continuous.  Various 
machines  using  liquids  as  the  working  medium  were  employed.  Un- 
til within  the  last  thirty  or  forty  years,  however,  refrigerating  ma- 
chines met  with  little  success,  the  inventors  in  most  cases  being 
compelled  to  stand  the  heavy  cost  of  development,  with  little  or  no 
returns.  An  interesting  point  in  connection  with  the  development  of 
mechanical  refrigeration,  is  seen  in  the  fact!  that  physicians  were  num- 
bered largely  in  the  list  of  those  developing  new  machines,  this  pre- 
sumably being  due  to  the  necessity  felt  in  medical  circles  for  cold 
water  and  ice  to  be  used  in  the  treatment  of  diseases.  Thus  the 
early  physicians  who  used  their  substance  in  an  effort  to  develop  a 
machine  to  alleviate  suffering,  were  philanthropic  heroes  of  the  first 
type. 

Air=  Machine.  About  1845,  Dr.  Gorrie  invented  the  cold-air 
refrigerating  machine,  which  was  later  developed  by  Windhausen, 
Bell,  Coleman,  Haslam,  and  others.  Thus  the  air-machine  invented 
by  a  physician  was  the  first  successful  refrigerating  machine  used  in 


REFRIGERATION  3 

commercial  work;  and  for  a  number  of  years  machines  constructed 
on  this  plan  were  used  exclusively  for  transporting  meats  and  perish- 
able products  over-sea.  This  was  the  first  large  application  of  me- 
chanical refrigeration.  On  account  of  the  advantages  incident  to 
the  absence  of  any  obnoxious  gases  in  the  cold-air  machine,  this 
type  of  refrigerating  apparatus  has  been  largely  used  on  shipboard 
even  to  the  present  day,  notwithstanding  the  fact  that  this  machine 
is  recognized  as  having  lower  mechanical  efficiency  than  other  types 
on  the  market. 

After  the  invention  of  Dr.  Gorrie,  the  next  important  step  in 
development  was  the  invention  of  the  ammonia  absorption  process, 
by  Carre",  in  1850;  and  between  1850  and  1860,  independent  inventors 
in  Australia  and  the  United  States  were  working  to  improve  the 
ether  machine  invented  by  Perkins  many  years  previously.  Machines 
of  this  type  were  put  in  commercial  use  in  Ohio  and  in  England  about 
1859. 

From  this  time  to  the  present  day,  there  has  been  no  question 
as  to  the  commercial  practicability  of  machines  for  producing  me- 
chanical refrigeration,  and  inventors  have  successively  brought  out 
various  designs  of  cold-air  compression  machines,  ammonia  and 
carbon  dioxide  machines  operating  on  the  compression  plan,  the 
ammonia  absorption  system,  and  the  dual  system  of  absorption 
refrigeration. 

Aside  from  this,  there  have  been  at  various  times  a  number  of 
special  machines  in  operation;  but  for  commercial  purposes  on  a 
large  scale,  the  proposition  has  narrowed  itself  down  to  a  choice  be- 
tween ammonia  or  carbon  dioxide  compression  machines  and  absorp- 
tion machines  using  ammonia  or  a  dual  liquid.  There  is  endless  dis- 
cussion among  engineers  as  to  which  of  these  two  systems  is  the  better, 
and  the  matter  seems  likely  not  to  be  settled  definitely  until  some 
radical  change  in  method  of  operation  or  design  is  made  in  one  or 
both  of  the  systems.  The  end  of  development  in  designing  and  con- 
structing refrigerating  machinery  is  not  yet;  and  progressive  men 
confidently  expect  to  see  marked  changes  in  the  recognized  procedure 
along  these  lines  at  no  very  distant  date. 

Definitions.  Refrigeration  may  be  defined  as  a  process  of 
cooling.  It  is  artifically  or  mechanically  performed  by  transferring 
the  heat  contained  in  one  body  to  another,  thereby  producing  a  con- 


4  REFRIGERATION 

dition  or  state  commonly  called  cold,  but  which  is  in  fact  an  absence 
of  heat.  The  terms  hot  and  cold  are  entirely  relative,  and  have  refer- 
ence to  the  manner  in  which  the  heat  of  substances  affects  the  senses. 
It  is  quite  possible  for  a  substance  that  feels  cold  to  one  person  to  feel 
hot  to  another,  so  that  the  terms  hot  and  cold  have  no  reference  what- 
ever to  the  absolute  amount  of  heat  in  a  given  substance.  One  sub- 
stance may  feel  colder  to  a  person  than  another,  and  yet  con- 
tain more  heat  than  the  substance  that  feels  warmer.  In  con- 
sidering a  transfer  of  heat  from  one  substance  to  another,  as 
in  a  refrigerating  machine,  the  student  should  bear  in  mind 
the  process  by  which  a  steam  engine  operates,  and  remember  that 
the  working  of  a  refrigerating  machine  is  exactly  the  reverse  of  en- 
gine operation. 

An  engine  converts  heat  into  mechanical  work,  while  the  refriger- 
ating machine  converts  mechanical  work  into  heat,  doing  this  in  such 
a  way  as  in  the  end  to  produce  cold.  It  thus  turns  out  that  in  order 
to  produce  cold  in  a  refrigerating  machine,  heat  must  be  expended; 
and  this  is  one  of  the  most  puzzling  points  that  the  uninitiated  man 
has  to  ponder  over  in  taking  up  a  study  of  refrigeration.  The  ex- 
planation is  found  in  the  first  law  of  thermodynamics,  which  states 
that  heat  and  work,  or  mechanical  energy,  are  mutually  convertible, 
and  that  heat  cannot  be  raised  from  a  lower  to  a  higher  level  of  tem- 
perature— as  in  passing  from  a  cold  to  a  hot  body — without  the  ex- 
penditure of  external  energy.  This  energy,  in  the  case  of  refrigera- 
ting machines,  is  finally  lost  in  the  cooling  water  that  passes  from  the 
condensers  and  other  parts  of  the  cooling  equipment  at  a  tempera- 
ture higher  than  when  brought  to  the  plant. 

By  the  expenditure  of  energy  in  performing  mechanical  work, 
heat  is  abstracted  from  one  substance  and  transferred  to  another  at 
a  higher  temperature;  and  the  substance  from  which  heat  is  taken 
then  becomes  cold  to  the  senses,  and  its  exact  temperature  or  sensible 
heat  is  determined  by  the  use  of  thermometers.  In  a  word,  then,  a 
refrigerating  machine  is  a  heat  pump;  and  in  studying  such  apparatus, 
it  becomes  necessary  to  learn  something  of  heat  and  the  units  used 
in  measuring  it,  as  well  as  the  method  of  effecting  its  measurement 
in  any  substance. 

Heat.  Unfortunately  scientists  have  never  been  able  to  deter- 
mine the  exact  nature  of  heat;  but  it  is  pretty  well  agreed  among 


REFRIGERATION  5 

authorities  that  heat  is  a  form  of  energy  manifesting  its  presence  in 
a  substance  by  producing  a  kind  of  motion  among  the  molecules  of 
which  the  substance  may  be  considered  as  made  up.  The  mole- 
cules are  supposed  to  be  separated  by  a  certain  distance  at  any  given 
temperature  of  the  substance,  this  distance  in  the  case  of  a  gas  being 
great  as  compared  to  the  size  of  the  molecules  themselves.  Molecules 
are  considered  as  being  round  and  as  being  in  rapid  vibratory 
motion,  which  motion  is  much  more  rapid  and  intense  as  the  tem- 
perature of  the  substance  rises  by  reason  of  the  addition  of  heat.  So 
long  as  the  kinetic  energy  manifesting  itself  in  this  motion  is  not  great 
enough  to  overcome  the  force  of  cohesion — which  exists  between  the 
molecules  of  all  substances  and  between  all  parts  of  the  universe — 
this  substance  retains  its  form;  but  as  soon  as  the  force  of  cohesion 
is  overcome,  there  is  a  change  of  state,  and  a  solid  substance  changes 
to  the  liquid  form,  or  a  liquid  to  the  gaseous  state.  On  the  other 
hand,  the  reverse  changes  in  state  take  place  when  the  substance  is 
cooled,  for,  as  the  temperature  falls,  the  vibratory  'motion  is  less 
intense,  and  the  distance  between  molecules  becomes  less,  until  the 
force  of  cohesion  acts  with  sufficient  effect  to  reduce  the  gaseous 
substance  first  to  the  liquid,  and  then,  as  the  temperature  continues 
to  fall,  to  the  solid  state. 

A  moment's  consideration  will  show  that  different  substances 
require  widely  different  changes  of  temperature  to  effect  a  change 
of  state.  Thus  metals  like  iron  fuse  or  melt  at  a  temperature  which 
will  vaporize  other  metals  like  zinc  and  tin.  This  temperature,  how- 
ever, is  many  degrees  higher  than  that  required  to  vaporize  liquid 
substances,  such  as  water,  which,  although  it  exists  in  the  solid 
form,  is  at  ordinary  temperature  a  liquid.  In  the  case  of  substances 
in  the  gaseous  form,  such  as  air,  a  comparatively  large  drop  in  tem- 
perature must  be  produced  by  refrigeration  before  the  force  of  co- 
hesion acts  with  sufficient  effect  to  reduce  the  gas  to  liquid  form. 
These  illustrations  of  the  manner  in  which  the  degree  of  heat  affects 
change  in  the  state  of  substances,  show  why  it  is  regarded  as  a  form 
of  energy  and  motion.  That  heat  is  not  a  material  substance,  is 
shown  conclusively  by  the  fact  that  the  weight  of  a  substance  is 
unchanged  no  matter  how  hot  or  cold  it  may  be,  and  that  a  given 
quantity  of  a  substance  will  retain  the  same  weight  in  the  liquid  01 
gaseous  state  as  when  existing  as  a  solid. 


6  REFRIGERATION 

Units  of  Heat  Measurement.  As  there  is  no  way  to  make  direct 
measurement  of  the  motion  of  molecules,  the  heat  in  a  given  amount 
of  substance  at  a  certain  temperature  cannot  be  measured  directly. 
It  can  be  measured  only  by  the  effect  produced  in  performing  work 
or  in  changing  the  state  of  some  other  substance.  It  is  therefore 
evident  that  the  measurement  of  energy  in  the  form  of  heat  is  an 
entirely  relative  or  comparative  process.  When  a  ball  of  iron  at  a 
certain  temperature  contains  enough  heat  to  melt  a  given  amount  of 
ice,  and  when  heated  to  another  temperature  melts  twice  as  much 
ice,  it  evidently  contains  twice  as  much  heat  energy  in  the  second 
case  as  in  the  first  instance.  For  convenience  in  practical  operation, 
scientists  have  established  an  arbitrary  heat  unit  by  which  all  amounts 
of  heat  may  be  measured,  this  unit  being  the  amount  of  heat  necessary 
to  raise  unity  weight  of  water,  at  its  maximum  density,  one  degree 
in  temperature.  Water  has  its  maximum  density  at  39.1  degrees 
F.  or  4  degrees  C.;  and  the  unit  of  measurement,  therefore,  is  the 
amount  of  heat  that  will  raise  one  pound  of  water  from,  39  to  40  degrees 
F.  or  from  4  to  5  degrees  C.,  the  former  being  the  British  thermal  unit, 
and  the  latter  the  thermal  unit.  For  convenience  it  is  customary 
to  use  the  letters  B.  T.  U.  as  an  abbreviation  for  the  first  of  these 
units;  and  unless  otherwise  specified,  all  heat  units  mentioned  in  the 
present  treatise  will  be  B.  T.  U.,  or  British  thermal  units. 

There  is  a  third  unit  used  in  France,  known  as  the  calorie,  which 
is  based  on  the  French  decimal  system  of  measurement.  A  calorie 
is  the  amount  of  heat  that  will  raise  the  temperature  of  one  kilogram 
of  water  from  4  to  5  degrees  C.  Since  one  degree  C.  is  9/5  of  a  degree 
F.  it  follows  that  the  thermal  unit  is  9/5  times  as  large  as  the  B.  T.  U. 
Also,  a  kilogram  is  the  same  as  2.2  pounds  of  water,  so  that  the  calorie 
is  the  same  as  2.2  thermal  units  or  3.96  B.  T.  U.  Each  of  these  units 
of  heat  measurement  has  reference  to  the  actual  amount  of  heat — or, 
in  other  words,  to  the  total  molecular  energy  in  a  substance — and 
has  no  reference  to  the  sensible  heat,  or  temperature,  of  the  substance. 

Sensible  heat,  or  temperature,  is  heat  as  manifested  to  our  senses 
by  a  substance,  and  is  determined  accurately  by  measuring  with  a 
thermometer.  We  feel  a  substance,  and  say  that  it  is  hotter  or  colder 
than  another  body  which  we  feel  at  the  same  time,  but,  owing  to  the 
imperfection  of  our  senses,  it  is  not  possible  to  determine  accurately 
just  how  much  hotter  or  colder  it  is.  Still  more  is  it  impossible  to 


REFRIGERATION  7 

ascertain  by  the  sense  of  touch  the  temperature  of  a  substance  taken 
alone.  It  is  because  of  this  imperfection  of  the  senses  that  the  instru- 
ments known  as  thermometers  are  used.  There  are  three  kinds  of 
these  instruments  in  use;  but  only  one  of  them  is  used  to  any  extent 
in  practical  work  in  the  United  States.  All  three  thermometers  are 
constructed  in  the  same  way  and  operate  on  the  same  principle,  the 
difference  consisting  solely  in  the  method  of  graduating  the  scales  of 
the  three  instruments. 

Measurement  of  temperature  or  sensible  heat  is  effected  in  all 
cases  by  noting  the  expansion  of  certain  substances  when  brought 
m  coutact  with  varying  amounts  of  heat.  Substances  used  for 
temperature  measurement  in  thermometers  may  be  in  any  one  of 
the  three  natural  states  of  matter — namely,  solid,  liquid,  or  gaseous; 
but  for  all  ordinary  work,  liquids  are  used,  the  expansion  in  the  case 
of  solids  being  too  small  with  ordinary  temperatures  to  be  readily 
measured  by  the  eye  on  a  thermometer  scale;  while,  on  the  other 
hand,  the  expansion  of  gases  is  far  too  large  for  such  measurement. 
In  order  that  the  thermometer  may  be  in  condition  for  use  at  all 
times,  it  is  essential  that  the  liquid  used  be  such  as  will  not  freeze  or 
change  into  the  gaseous  form  at  the  ordinary  temperatures  for  which 
the  instrument  is  designed  to  be  used.  Two  materials  that  have 
been  found  to  satisfy  these  requirements  are  mercury  and  alcohol, 
the  former  of  these  being  used  because  it  does  not  boil  except  at  a 
very  high  temperature,  while  alcohol,  on  the  other  hand,  freezes  at 
such  a  low  temperature  (  — 203F.)  that  it  may  be  used  in  the  thermom- 
eters for  refrigeration.  Only  one  of  these  substances,  generally,  is  used 
in  a  single  thermometer;  but  in  the  case  of  instruments  designed  for 
automatically  recording  maximum  and  minimum  temperatures,  tubes 
using  the  two  liquids  on  the  same  instrument  are  employed.  As  alcohol 
boils  at  172.4°  F.,  it  cannot  be  used  for  high-temperature  work,  and  is 
suitable  only  in  cold  stores  and  other  places  where  low  temperatures 
are  to  be  recorded. 

Much  skill  is  required  to  make  accurate  thermometers,  and  great 
care  must  be  taken  in  graduating  the  scale  on  the  tube.  Cheap 
thermometers  having  the  scale  on  the  frame  carrying  the  mercury 
tube  are  of  little  or  no  value  in  careful  work,  and  it  is  always  prefer- 
able to  use  instruments  having  the  graduations  on  the  glass  itself. 
Even  then,  in  making  the  graduations  allowances  must  be  made 


8  REFRIGERATION 

for  the  expansion  of  the  glass  at  different  temperatures  and  for  the 
fact  that  the  bore  of  the  tube  cannot  be  depended  on  to  have  a 
uniform  size. 

Having  sealed  the  mercury  in  its  tube,  the  next  step  in  making 
a  thermometer  is  to  determine  the  fixed  points,  the  lower  one  being 
that  point  in  the  tube  at  which  the  mercury  stands  when  placed  in 
melting  ice,  and  the  higher  fixed  point  being  that  at  which  the  mer- 
cury stands  when  placed  above  water  boiling  under  standard  pres- 
sure. When  these  two  points  have  been  determined  and  etched  on 
the  tube,  the  graduation  of  the  space  between  is  a  matter  of  calcula- 
tion and  measurement,  taking  care  that  allowances  are  made  for  all 
irregularities  of  the  tube. 

There  are  three  methods  of  graduating  thermometer  scales, 
known  respectively  as  the  Fahrenheit,  Centigrade,  and  Reaumur,  the 
names  being  taken  from  the  inventors  of  the  respective  methods.  It 
is  customary  to  use  the  initial  letters — F.,  C.,  and  R. — of  these  names 
as  abbreviations,  as  has  already  been  done  in  this  text.  Where  tem- 
peratures below  the  zero  point  of  a  scale  are  denoted,  the  subtraction 
or  minus  sign  of  arithmetic  is  placed  before  the  figure  denoting  the 
number  of  degrees.  Thus,  —  5  F.  would  mean  five  degrees  below 
the  zero  point  on  the  Fahrenheit  scale.  On  this  scale,  the  freezing 
point  of  water  is  marked  32  degrees,  the  zero  point  consequently 
being  32  degrees  below  freezing.  At  sea-level,  water  under  atmos- 
pheric pressure  boils  at  212  degrees  F.,  while  the  absolute  zero  point 
of  the  scalene.,  the  point  at  which  there  is  no  molecular  motion  of  any 
•substance,  is  460.6  (approximately  461)  degrees  below  zero,  or  492.6 
(approximately  493)  degrees  below  the  point  at  which  water  freezes. 
Experimenters  have  never  been  able  to  reduce  the  temperature  of 
any  substance  to  absolute  zero  (that  is,  to  abstract  all  the  heat  energy 
from  any  substance);  and  the  figure  named  is  not  from  positive 
measurement,  but  the  result  of  calculations  made  on  the  behavior 
of  gases.  For  one  degree  F.,  a  perfect  gas  will  expand  or  contract 
about  1/493  part  of  its  volume;  and  for  one  degree  C.,  the  change 
in  volume  is  about  1/273  part.  This,  taken  in  connection  with  the 
conception  of  heat  as  the  manifestation  of  the  energy  of  molecular 
motion,  directly  proportional  to  the  expansion  or  contraction  of  a 
substance,  gives- 493°  F.  and  273°  C.  as  the  points  on  the  respec- 
tive scales  at  which  there  would  be  no  molecular  motion.  Some  idea 


REFRIGERATION  9 

of  the  intense  cold  at  absolute  zero  may  be  had  by  considering  the 
fact  that  melting  ice  is  as  much  warmer  than  any  substance  at  the 
absolute  zero  point  as  molten  solder  is  warmer  than  the  ice. 

On  the  Centigrade  scale,  the  freezing  point  of  water  is  marked 
"0,"and  the  boiling  point  "100,"  the  interval  being  divided  into  one 
hundred  degrees.  This  scale  is  universally  employed  in  scientific 
work,  there  being  many  advantages  incident  to  the  use  of  the  decimal 
system  in  calculations.  The  Reaumur  scale  also  has  the  freezing 
point  at  zero,  but  the  boiling  point  is  marked  "80."  This  scale  is 
used  in  some  parts  of  Europe,  particularly  in  brewery  work,  but  has 
little  to  recommend  it.  It  is  seen  that  180  degrees  on  the  F.  scale 
corresponds  to  100  degrees  C.,  so  that  1  degree  C.  is  9/5  degree  F. 
To  change  a  Fahrenheit  temperature  to  Centigrade,  subtract  32 
degrees,  and  multiply  the  result  by  5/9.  To  charfge  C.  to  F.,  mul- 
tiply by  9/5,  and  add  32  degrees.  Table  I,  page  10,  gives  a  compari- 
son of  the  three  thermometer  scales;  by  reference  to  this  table,  the 
labor  of  calculation  may  be  avoided. 

The  specific  heat  of  a  body  or  substance  is  its  capacity  for  ab- 
sorbing heat,  as  compared  with  the  capacity  of  water.  Thus,  in 
this  case  also,  the  measurement  of  heat  is  relative,  being  referred  to 
the  heat-absorbing  capacity  of  water  as  the  unit.  As  the  specific 
heat  of  a  unit  weight  of  water  is  taken  as  unity,  the  specific  heat  of 
other  substances  is  less  than  unity,  being  smaller  than  the  unit  in  almost 
every  case.  It  has  already  been  shown  that  the  unit  of  absolute 
heat  measurement  (B.  T.  U.)  is  the  amount  of  heat  that  will  raise 
the  temperature  of  1  pound  of  water  1  degree  F.  at  the  temperature 
of  maximum  density;  and  as  the  specific  heats  of  other  substances 
are  less  than  that  of  water,  we  may  define  the  specific  heat  of  any 
substance  as  being  that  proportion  of  a  B.  T.  U.  which  is  required 
to  raise  the  temperature  of  one  pound  of  the  substance  one  degree. 

There  is  some  variation  in  the  amount  of  heat  required  to  raise 
the  temperature  of  a  substance  one  degree  at  different  temperatures; 
but  for  practical  purposes  in  refrigeration,  this  may  be  neglected, 
the  difference  being  of  importance  only  for  those  engaged  in  minute 
scientific  calculations.  It  is  worth  noting,  however,  that  this  varia- 
tion must  be  considered  in  dealing  with  the  specific  heat  of  gases, 
as  in  this  case  it  is  of  considerable  importance,  the  specific  heat  of 
the  gas  varying  by  quite  appreciable  amounts  under  different  con- 


10 


REFRIGERATION 


TABLE  I 
Thermometer  Scales 


FAHR. 

CENT. 

REAU. 

FAHR. 

CENT. 

REAU. 

FAHR. 

CENT. 

REAU. 

212 

100 

80 

120 

48.9 

39.1 

30 

—  1.1 

—  0.9 

210 

98.9 

79.1 

118 

47.8 

38.2 

28 

-  2.2 

-  1.8 

208 

97.8 

78.2 

116 

46.7 

37.3 

26 

-  3.3 

—  2.7 

206 

96.7 

77.3 

114 

45.6 

36.4 

24 

—  4.4 

—  3.6 

204 

95.6 

76.4 

112 

44.4 

35.6 

22 

-  5.6 

—  4.4 

202 

94.4 

75.6 

110 

43.3 

34.7 

20 

—  6.7 

—  5.3 

200 

93.3 

74.7 

108 

42.2 

33.8 

18 

—  7.8 

—  6.2 

198 

92.2 

73.8 

106 

41.1 

32.9 

16 

—  8.9 

-  7.1 

196 

91.1 

72.9 

104 

40 

32 

14 

—10 

—  8 

194 

90 

72 

102 

38.9 

31.1 

12 

—11.1 

—  8.9 

192 

88.9 

71.1 

100 

37.8 

30  2 

10 

j2  2 

—  9.8 

190 

87.8 

70.2 

98 

36.7 

29.3 

8 

—13^3 

—10.7 

188 

86.7 

69.3 

96 

35.6 

28.4 

6 

—14.4 

—11.6 

186 

85.6 

68.4 

94 

34.4 

27.6 

4 

—15.6 

—12.4 

184 

84.4 

67.6 

92 

33.3 

26.7 

2 

—16.7 

—13.3 

182 

83.3 

66.7 

90 

32.2 

25.8 

6 

—17.8 

—14.2 

180 

82.2 

65.8 

88 

31.1 

24.9 

—  2 

—18.9 

—15.1 

178 

81.1 

64.9 

86 

30 

24 

—  4 

—20 

—16 

176 

80 

64 

84 

28.9 

23.1 

—  6 

—21.1 

—16.9 

174 

78.9 

63.1 

82 

27.8 

22.2 

—  8 

—22.2 

—17.8 

172 

77.8 

62.2 

80 

26.7 

21.3 

—10 

—23.3 

—18.7 

170 

76.7 

61.3 

78 

25.6 

20.4 

—12 

—24.4 

—19.6 

168 

75.6 

60.4 

76 

24.4 

19.6 

—14 

—25.6 

—20.4 

166 

74.4 

59.6 

74 

23.3 

18.7 

—16 

—26.7 

—21.3 

164 

73.3 

58.7 

72 

22.2 

17.8 

—18 

—27.8 

—22.2 

162 

72.2 

57.8 

70 

21.1 

16.9 

—20 

—28.9 

—23.1 

160 

71.1 

56.9 

68 

20 

16 

—22 

—30 

—24 

158 

70 

56 

66 

18.9 

15.1 

—24 

—31.1 

—24.9 

156 

68.9 

55.1 

64 

17.8 

14.2 

—26 

^2  2 

—25.8 

154 

67.8 

54.2 

62 

16.7 

13.3 

—28 

—33^3 

—26.7 

152 

66.7 

53.3 

60 

15.6 

12.4 

—30 

—34.4 

—27.6 

150 

65.6 

52.4 

58 

14.4 

11.6 

—32 

—35.6 

—28.4 

148 

64.4 

51.6 

56 

13.3 

10.7 

—34 

—36.7 

—29.3 

146 

63.3 

50.7 

54 

12.2 

9.8 

—36 

—37.8 

—30.2 

144 

62.2 

49.8 

52 

11.1 

8.9 

—38 

—38.9 

—31.1 

142 

61.1 

48.9 

50 

10 

8 

—40 

—40 

—32 

140 

60 

48 

48 

8.9 

7.1 

—42 

—41.1 

—32.9 

138 

58.9 

47.1 

46 

7.8 

6.2 

—44 

—42.2 

—33.8 

136 

57.8 

46.2 

44 

6.7 

5.3 

—46 

—43.3 

—34.7 

134 

56.7 

45.3 

42 

5.6 

4.4 

—48 

—44.4 

—35.6 

132 

55.6 

44.4 

40 

4.4 

3.6 

—50 

—45.6 

—36.4 

130 

54.4 

43.6 

38 

3.3 

2.7 

—52 

—46.7 

—37.3 

128 

53.3 

42.7 

36 

2.2 

1.8 

—54 

—47.8 

—38.2 

126 

52.2 

41.8 

34 

1.1 

0.9 

—56 

—48.9 

—39.1 

124 

51.1 

40.9 

32 

0 

0 

—58 

—50 

—40 

122 

50 

40 

ditions  of  pressure  and  volume  as  brought  about  by  varying  tem- 
perature. As  the  capacity  of  a  substance  for  absorbing  heat  is 
determined  directly  by  its  specific  heat,  and  as  all  refrigerating  work 
is  done  to  dispose  of  the  heat  absorbed  by  substances,  it  is  evident 


REFRIGERATION  11 

at  once  that  a  knowledge  of  the  specific  heats  of  various  substances 
is  of  first  importance  to  those  concerned  with  refrigerating  work. 

Aside  from  leakage  and  conduction  losses,  the  refrigeration  that 
must  be  performed  in  any  case  depends  directly  on  the  specific  heat 
of  the  substance  to  be  cooled;  and  it  is  on  account  of  this  fact  (hat 
scientists  and  practical  refrigerating  men  have  devoted  a  great  deal 
of  time  and  attention  to  the  accurate  determination  of  the  specific 
heat  of  all  substances  and  materials  ordinarily  handled  in  refrigera- 
ting establishments. 

Owing  to  the  inherent  difficulty  in  determining  the  specific  heat 
of  a  subtance,  values  obtained  by  independent  investigators  have  been 
found  at  times  to  differ,  but  Table  II  gives  the  figures  commonly 
accepted  for  a  number  of  the  more  important  substances,  while 
Table  III  gives  the  specific  heat  and  the  specific  gravity  of  beer 
wort.  By  the  use  of  these  tables,  it  is  possible  to  calculate  in  any  given 
case  the  amount  of  refrigeration  that  will  be  required  to  handle  a 
knowTn  quantity  of  goods,  the  leakage  of  heat  through  the  in- 
sulating material  of  the  cold  stores  being  previously  determined  by 
experiment. 

Latent  heat  is  a  term  used  to  designate  the  quantity  of  heat 
absorbed  or  given  up  by  a  substance  to  effect  change  of  state  without 
a  change  of  temperature.  Thus  one  pound  of  ice  at  32  degrees,  on 
being  melted  into  water  at  the  same  temperature,  absorbs  142.65 
heat  units;  and  one  pound  of  water  at  212  degrees,  when  evaporated 
into  steam  at  the  same  temperature,  absorbs  966.6  units.  It  is  this 
absorption  of  heat  on  change  of  state  that  causes  cooling  by  the 
evaporation  of  water  and  other  liquids.  For  each  pound  of  water 
evaporated  at  atmospheric  pressure,  about  966  B.  T.  U.  are  absorbed, 
and  become  latent  in  the  vapor  passing  off  from  the  water.  This 
heat  must  be  taken  up  from  the  surrounding  objects,  which  are  thereby 
cooled.  One  pound  of  water  evaporated,  then,  is  sufficient  to  cool  966 
pounds  of  water  one  degree.  This  is  the  principle  used  in  all  practical 
refrigerating  machines  of  the  present  time ;  but  it  is  impracticableto  use 
water  for  the  evaporating  liquid,  on  account  of  the  fact  that  it  boils 
at  a  comparatively  high  temperature,  the  temperature  at  atmospheric 
pressure  being  212  degrees  F.,  while  that  of  liquid  ammonia, 
for  example,  at  the  same  pressure  is  —  28  degrees.  This  is  the  main 
reason  why  ammonia  is  used  so  largely  in  refrigerating  work,  in  spite 


12 


REFRIGERATION 


TABLE  II 
Specific  Heat  of  Various  Substances  Under  Constant   Pressure 

SOLIDS 


Copper  
Gold 

0.0951 
0  0324 

Cast  Iron  
Lead 

.0.1298 
0  0314 

0  1138 

Platinum 

0  0324 

Steel  (soft) 

0  1165 

Silver 

0  0570 

Steel  (hard"1 

0  1175 

Tin 

0  0562 

Zinc  

0.0956 

Ice  

.0.5040 

Brass  

0.0939 

Sulphur  

.0.2026 

Glass  
Oak.  

0.1937 
0.570 

Charcoal  
Brickwork  

.0.2410 
.0.200 

Pine  

0.650 

Stone  

.0.270 

Cast  Iron  
Coal  
Coke  
Fish  
Chicken  
Eggs  

0.130 
0,241 
0.203 
0.70 
0.80 
0.76 

Marble  
Fat  Beef  
Lean  Beef  
Fat  Pork  
Veal  
Fruit  and  Vegetables 

.0.209    toO 
.0.60 
.0.77 
.0.51 
.0.70 
.0.50      toO 

215 

93 

LIQUIDS 


Water 

1  0000 

Milk 

0  90 

Alcohol 

0  7000 

Lead  (melted). 

0  0402 

Mercury  
Benzine  
Glycerine  
Strong  Brine  
Vinegar 

0.0333 
0.4500 
0.5550 
0.700 
0  920 

Sulphur  (melted)  
Tin  (melted)  
Sulphuric  Acid  
Oil  of  Turpentine  
Anhydrous  Ammonia 

0.2340 
0.0637 
0.3350 
0.4260 
1  020 

Cream  

0.680 

Carbonic  Acid  

0.980 

GASES 


CONSTANT  PRESSURE 

CONSTANT  VOLUME 

Air 

0  23751 

0    16847 

Oxvsen 

0  21751 

0    15507 

Nitrogen 

0  24380 

0  17273 

Hydrogen  

3.40900 

2.41226 

Superheated  Steam  
Carbonic  Oxide 

0.48050 
0  24790 

0.34600 
0  17580 

Carbonic  Acid 

0  21700 

r     o  15350 

Ammonia 

0  393 

0  508 

of  the  fact  that  its  latent  heat  is  but  little  more  than  half  that  of  water 
(or  573  B.  T.  U.)  when  expanded  at  atmospheric  pressure. 

The  temperature  at  which  a  solid  changes  to  the  liquid  form  is 
known  as  its  temperature  of  fusion;  and  that  at  which  it  passes  into 
the  form  of  vapor,  is  known  as  the  temperature  of  vaporization. 
Similarly,  we  have  the  terms  latent  heat  of  fusion  and  latent  heat  of 


REFRIGERATION 


13 


vaporization,  or  the  heat  required  in  each  case  to  effect  the  change 
in  state  of  the  substance  without  changing  its  temperature. 

Table  IV  gives  the  temperatures  and  latent  heats  of  fusion  and 
vaporization  for  a  number  of  substances  for  which  this  data  has  been 
determined  by  experiment.  It  will  be  noticed  from  the  blank  spaces 
in  the  table,  that  considerable  is  yet  to  be  learned  on  this  subject  in 
regard  to  some  substances.  Thus,  for  example,  the  temperature 
at  which  alcohol  may  be  changed  to  the  solid  form  has  never  been 

TABLE  III 
Specific  Heat  and  Specific  Gravity  of  Beer  Wort 


N 

o 

OH 

OH 

0 

Q  £ 

C*  H 

1*1 

KM 

I* 

**g 

a  55  j 

i| 

!» 

o"m 

8* 

O^ffl 

2  w 

QJ  B* 

82 

sB 

a  M  M 

[5  U 

S5 

«    M 

K  0 

W     Q    y 

K  £ 

Ht>*  H 

Ss 

s« 

nfe  ^ 

5g 

tf  U 

•< 

o  a 

£}  A, 

QO 

O  "" 

< 

02 

°t» 

8 

1  .0320 

.944 

15 

1.0614 

.895 

9 

1  .0363 

.937 

16 

1  .0657 

.888 

10 

1  .0404 

.930 

17 

1.0700 

.881 

11 

1.0446 

.923 

18 

1  .0744 

.874 

12 

1  .0488 

.916 

19 

1  .0788 

.867 

13 

1  .0530 

.909 

20 

1  .0832 

.861 

14 

1  .0572 

.902 

determined,  as  no  process  has  ever  been  devised  for  freezing  this 
liquid.  Then,  again,  the  vaporization  of  tin  and  lead  takes  place  at 
such  high  temperatures  as  to  make  accurate  measurement  impossible 
by  any  known  means  of  recording  temperatures. 

Unit  of  Plant  Capacity.  Ordinarily  the  capacity  of  a  refrigera- 
ting machine  or  plant  is  stated  in  tons — that  is,  one  ton  is  the  heat 
equivalent  of  a  2,000-pound  ton  of  ice  at  32  degrees  F.,  melted  into 
water  at  the  same  temperature;  or,  conversely,  the  amount  of  heat  that 
must  be  abstracted  from  2,000  pounds  of  water  at  32  degrees  to  change 
it  into  ice  at  the  same  temperature.  Since  the  latent  heat  of  ice  is  about 
142  B.  T.  U  ,  the  ton  of  refrigerating  capacity  used  in  rating  apparatus 
is  equivalent  to  142  X  2,000  =  284,000  B.  T.  U. 

Thermodynamics,  as  the  name  implies,  is  the  science  treating  of 
heat  as  a  form  of  energy  and  of  its  relation  to  other  forms  of  energy, 
particularly  its  relation  to  and  transformation  into  mechanical  energy 


14 


REFRIGERATION 


TABLE  IV 
Fusion  and  Vaporization  Data  of  Substances 


SUBSTANCE 

TEMPERA- 
TURE  OF 
FUSION 
F. 

TEMPERA- 
TURE   OF 
VAPORIZA- 
TION 
F. 

LATENT 
HEAT   OF 
FUSION 

LATENT 
HEAT  OF 
VAPORIZA- 
TION 

Water  

32° 

212° 

142.65 

966.6 

Mercury  

-37.8° 

662° 

5.09 

157 

Sulphur  
Tin 

228.3° 
446° 

824° 

13.26 
25.65 

Lead'.......'..  ......... 

626° 

9.67 

Zinc  

680° 

V,900° 

50.63 

493 

Alcohol  

Unknown 

173° 

372 

Oil  of  Turpentine  
Linseed  Oil  

14° 

313° 
600° 

124 

Aluminum  

1,400° 

Copper  

2,100C 

Cast  Iron  

2,192° 

3,300° 

Wrought  Iron  

2,912° 

5,000° 

Steel  

2,520° 

Platinum  

3,632° 

Iridium    .           

4,892° 

or  work.  It  is  not  possible  in  brief  space  to  enter  into  a  discussion 
of  thermodynamics  in  detail;  but  brief  mention  must  be  made  of  the 
fundamental  principles  of  this  science  that  have  to  do  with  the  opera- 
tion of  refrigerating  apparatus. 

Some  reference  has  already  been  made  to  the  first  law,  which 
is  a  special  case  of  the  general  law  expressing  the  mutual  converti- 
bility of  all  forms  of  energy.  According  to  this  law,  as  already 
mentioned,  heat  is  equivalent  to  work  or  mechanical  energy,  each 
unit  of  heat  being  equivalent  to  778  foot-pounds  of  work,  or  the 
amount  of  work  that  must  be  performed  to  raise  778  pounds  a  vertical 
distance  of  one  foot  against  the  action  of  gravity.  This  first  law  of 
thermodynamics  must  be  qualified  to  some  extent,  for,  although 
heat  and  work  when  convertible  are  theoretically  equivalent  to  each 
other,  the  actual  conversion  of  one  into  the  other  is  not,  in  every  case 
practicable — being,  in  fact,  practicable  in  every  case  only  so  far  as 
the  conversion  of  work  into  heat  is  concerned.  In  other  words,  while 
it  is  always  possible  to  change  a  given  amount  of  work  into  heat 
energy,  it  is  not  possible  in  every  case  to  convert  heat  into  work,  for 
there  is  always  a  certain  amount  of  unavailable  heat  which  it  is 
found  impracticable,  with  devices  at  present  in  use,  to  convert  into 
work. 


REFRIGERATION  15 

The  second  law  of  thermodynamics  states,  therefore,  that  it  is 
impossible  to  transfer  heat  from  a  body  of  low  temperature  to  one 
of  higher  temperature  without  the 'application  of  some  external  form 
of  energy. 

Thus  in  every  case,  for  a  given  temperature,  there  is  a  certain 
well-defined  portion  of  the  total  heat  in  the  substance  that  can  be 
converted  into  work,  the  remaining  heat  being  unavailable  for  con- 
version. If  this  were  not  true,  it  would  be  possible  to  reduce  the 
temperature  to  absolute  zero,  when  the  substance  would  have  no 
volume.  Thus  matter  would  be  annihilated.  As  this  is  impossible, 
however,  it  is  plain  that  absolute  zero  temperature  can  never  be 
attained.  In  every  case  where  heat  is  converted  into  work,  there  is 
a  lowering  of  the  temperature  of  the  body  from  which  the  heat  is 
taken,  and  the  fall  in  temperature  is  an  index  of  the  amount  of  heat 
energy  converted  into  work.  The  energy  existing  as  heat  at  low 
temperature  is  unavailable  and  must  be  dissipated,  it  being  absorbed 
on  discharge  from  the  heat  engine  by  a  still  colder  body,  which  in 
the  case  of  steam  engines  is  the  atmosphere  or  condensing  water. 
Much  depends  on  the  character  of  the  heat  engine,  as  to  just  what 
amount  of  energy  in  the  form  of  heat  will  be  transformed  into  useful 
work.  A  conspicuous  example  of  this  is  the  case  of  low-pressure 
turbines,  which,  within  the  last  few  months,  have  been  so  perfected 
as  to  reclaim  as  much  energy  from  the  exhaust  steam  of  reciprocating 
engines  as  the  engines  themselves  utilize  in  the  first  place. 

As  already  pointed  out,  the  molecular  activity  of  a  substance 
is  increased  by  heating  or  raising  its  temperature;  and  it  is  this  molec- 
ular activity  that  gives  an  index  to  the  energy  present  and  available 
in  the  form  of  heat.  There  are  many  ways  of  converting  this  energy 
into  work;  but,  in  that  most  commonly  used,  advantage  is  taken  of 
the  pressure  produced  by  the  molecular  activity  of  a  gas  that  has  been 
heated.  The  gas  in  its  heated  state  is  placed  behind  a  piston;  and 
the  molecules  in  their  efforts  to  get  away  from  each  other,  or  to  occupy 
a  larger  space,  exert  a  pressure  on  the  piston  that  moves  it  forward. 
As  the  gas  expands,  its  heat  energy  is  expended,  and  its  temperature 
is  lowered  until  the  force  of  cohesion  acting  between  the  molecules 
is  sufficient  to  prevent  the  performance  of  further  external  work. 
The  one  condition  of  work  being  performed  is,  that  there  shall  be 
resistance  to  movement  of  the  piston — there  being  no  work,  with 


16  REFRIGERATION 

resulting  fall  of  temperature,  where  a  gas  has  free  room  to  expand, 
as  in  a  vacuum. 

This  leads  to  a  consideration  of  the  way  in  which  gases  may  be 
compressed  and  expanded ;  and  it  is  well  for  the  student  to  give  atten- 
tion to  this  subject  which  lies  at  the  bottom  of  all  efficient  work  in 
refrigerating  machines.  When  a  gas  is  expanded  or  compressed 
without  addition  or  subtraction  of  heat,  the  process  is  said  to  be 
adiabatic,  and  the  temperature  of  the  gas  will  rise  with  compression 
and  fall  with  expansion.  If  it  is  desired  to  maintain  the  temperature 
of  the  gas  constant,  heat  must  be  abstracted  as  the  gas  is  compressed, 
or  supplied  as  it  is  expanded,  except  in  the  case  of  free  expansion, 
in  which  case  there  is  practically  no  change  in  temperature.  In  this 
discussion,  however,  it  is  assumed  that  work  is  expended  in  compress- 
ing the  gas,  and  that  the  gas  performs  work  in  expanding. 

As  the  heat  abstracted  from  a  gas  in  a  heat  engine  is  the  equiv- 
alent of  the  work  performed,  it  should  be  possible  theoretically  to 
restore  the  temperature  of  the  gas  to  its  original  state  by  reversing  the 
operation  of  the  heat  engine,  there  being  no  loss  of  heat  in  the  process. 
In  practical  work,  a  certain  part  of  the  work  obtained  from  heat  in 
an  engine  is  dissipated  at  once  in  overcoming  the  frictional  resistance 
of  the  moving  parts  of  the  machine,  and  appears  as  heat  in  the  bear- 
ings, etc.,  so  that  the  theoretical  conditions  of  a  complete  reversible 
cycle  cannot  be  carried  out.  If  it  were  possible  to  convert  heat  into 
mechanical  work  by  direct  process  without  the  intervention  of  heat 
engines  or  other  mechanism,  there  would  be  much  greater  efficiency 
than  at  present;  but  so  far  no  method  of  doing  this  has  been  found. 
Where  a  gas  is  allowed  to  expand  freely  without  performing  work,  its 
energy  is  dissipated,  and  there  is  no  way  to  restore  it  to  its  original 
condition  without  the  expenditure  of  some  external  form  of  energy. 
It  is  possible,  therefore,  for  the  entire  heat  energy  of  the  world  to  be 
dissipated,  as  the  only  way  in  which  waste  heat  is  reclaimed  is  in  its 
indirect  effect  on  growing  vegetable  matter  which  can  be  used  as  fuel. 

In  the  operation  of  a  refrigerating  machine,  it  is  necessary  to 
have  a  continuous  conversion  of  heat  into  work.  This  presupposes 
dissipation  of  a  certain  amount  of  heat  energy,  as  it  is  impossible  to 
carry  on  continuous  conversion  without  the  loss  of  the  unavailable 
heat  that  must  be  rejected  by  the  machine.  Thus  the  heat  pump 
of  a  refrigerating  establishment  is  a  machine  designed  to  abstract  a 


REFRIGERATION  17 

certain  amount  of  heat  from  the  body  to  be  cooled  by  changing  the 
form  of  the  surrounding  medium  used  in  the  abstraction  so  that  its 
temperature  becomes  lower  than  that  of  the  body  itself.  It  is  there- 
fore evident  that,  with  the  possible  exception  of  the  vacuum  pro- 
cess, in  which  the  evaporation  of  a  portion  of  a  body  of  water 
absorbs  sufficient  heat  to  freeze  the  remaining  part  of  the  water, 
it  is  impossible  for  a  machine,  however  designed,  to  refrigerate 
the  body  to  be  cooled  without  using  some  working  medium.  Several 
kinds  of  mediums  are  used,  and  will  be  discussed  in  detail  later. 

In  practically  all  cases,  water  is  used  for  the  cooling  body  to 
absorb  the  waste  heat,  the  water  being  circulated  over  the  condensers 
and  cooling  coils  of  the  machine,  so  as  to  take  up  the  heat  that  has 
been  concentrated  in  a  comparatively  small  volume  of  the  working 
medium  by  the  action  of  the  refrigerating  machine.  It  is  therefore 
in  order  to  see  how  the  machine  effecting  this  result  is  constructed; 
but  before  doing  this,  it  is  well  to  see  in  what  way  heat  transfers  are 
made. 

Heat  transfers  may  be  made  in  three  ways — by  radiation,  by 
convection,  and  by  conduction.  An  illustration  of  the  meaning  of  these 
terms  is  had  in  the  case  of  an  iron  bar  thrust  into  the  fire  until  one  end 
becomes  hot.  When  the  bar  is  withdrawn  from  the  fire,  it  loses  heat 
in  each  of  the  three  ways  mentioned,  part  of  the  heat  being  radiated 
into  space,  part  of  it  being  conducted  along  the  length  of  the  bar, 
and  part  being  carried  off  by  air  currents  which  circulate  around  the 
bar,  the  heated  air  rising.  At  first  the  temperature  of  the  iron 
will  fall  rapidly ;  but  as  it  becomes  cooler,  the  transfer  of  heat 
to  the  atmosphere  and  surrounding  objects  becomes  less  rapid. 
This  brings  us  to  the  law  of  Newton,  which  holds  good  for  mod- 
erate temperatures  such  as  those  used  in  refrigerating  work — 
namely : 

"The  rate  of  cooling  of  a  body  is  proportional  to  the  difference  between 
the  temperature  of  its  surface  and  that  of  its  surroundings." 

In  the  case  of  liquids,  we  have  the  similar  law,  also  evolved  by 
Newton,  in  the  words : 

"The  amount  of  heat  lost  in  a  given  interval  of  time  by  a  vessel  filled 
with  liquid  is  proportional  to  the  mean  difference  of  temperature  between  th*> 
liquid  and  its  surroundings." 


18  REFRIGERATION 

Radiation.  Taking  again  the  illustration  of  the  hot  bar  of  iron, 
if  the  hand  is  placed  at  a  certain  distance  above  the  bar,  a  greater 
intensity  of  heat  is  felt  than  if  it  is  placed  at  the  same  distance  below 
the  bar,  this  being  due  to  the  fact  that  in  the  first  case  the  hand  feels 
heat  emitted  from  the  bar  both  by  radiation  and  convection,  while  in 
the  second  case  with  the  hand  underneath  the  bar,  the  heat  or  radia- 
tion alone  is  felt.  Another  illustration  of  radiant  heat  is  the  common 
experiment  performed  with  the  optical  lens  by  means  of  which  the 
rays  are  focused  on  a  given  point,  when  the  heat  becomes  so  intense 
as  to  burn  the  flesh  or  ignite  a  dry  substance.  Radiant  heat  rays 
pass  readily  through  glass,  but  are  reflected  by  smooth  polished 
surfaces;  while,  on  the  other  hand,  a  rough  surface  covered  with  lamp 
black  will  absorb  the  rays.  The  rays"  pass  readily  through  air,  but 
are  absorbed  to  some  extent  by  carbonic  acid  gas,  and  still  more  so 
by  ammonia  gas. 

A  warm  body  exposed  to  the  air  will  lose  a  certain  amount  of  its 
heat  by  radiation;  but  when  placed  in  a  closed  chamber  the  walls 
of  which  are  at  the  same  temperature  as  itself,  will  lose  no  heat. 
This  does  not  mean,  however,  that  radiation  of  heat  from  the  body 
stops  under  such  circumstances,  but  simply  that  as  much  heat  is 
radiated  from  the  walls  of  the  containing  chamber  to  the  body  as  is  radi- 
ated from  the  body  to  the  walls,  so  that  the  temperature  of  walls  and 
body  remains  constant.  This  is  known  as  Prevost's  theory  of  radiant 
heat  exchanges;  and  in  the  case  cited,  the  radiation  of  heat  is  equal 
from  the  body  and  from  the  walls.  Where  bodies  are  at  different 
temperatures,  the  exchange  of  radiant  heat  goes  on  in  the  same  man- 
ner; but  the  amount  radiated  from  the  warmer  body  is  greater  than 
that  from  the  cooler  body,  so  that  there  is  a  tendency  to  equalize  the  • 
temperatures  of  the  two  bodies. 

Where  two  bodies  covered  with  lamp-black  are  enclosed  in  a 
chamber  the  walls  of  which  are  at  the  same  temperature  as  the  bodies, 
the  temperatures  throughout  will  remain  constant;  but  as  the  black 
surface  of  one  body  will  absorb  heat  readily  and  this  heat  must  be 
supplied  from  external  sources,  it  is  evident  that  the  other  body  must 
emit  heat  rapidly.  In  other  words,  the  exchange  process  of  radiant 
heat  goes  on  much  more  rapidly  between  bodies  covered  with  lamp- 
black— and,  in  general,  between  all  dark  bodies — than  between 
bodies  of  lighter  color  and  those  that  are  polished.  Thus  good 


REFRIGERATION  19 

absorbers  of  heat  are  also  good  radiators;  and  surfaces  designed  to 
absorb  or  radiate  heat  should  preferably  be  of  a  dark  color,  while 
those  designed  to  prevent  radiation  should  be  smooth  and  of  as  light 
color  as  practicable  Thus  a  polished  copper  steam  pipe  radiates 
much  less  heat  than  a  similar  black  pipe,  and  a  pL:n  cast-iron  radiator 
is  better  than  the  same  radiator  covered  with  one  of  the  bright  metallic 
paints  so  frequently  used.  For  this  reason,  also,  the  walls  and  sides 
of  a  cold  storage  house  should  be  whitewashed  or  constructed  of 
white  enamel  brick  to  reflect  radiant  heat  that  otherwise  would  be 
absorbed  by  the  walls  and  conducted  through  the  insulating  material 
of  the  rooms  to  the  cold  stores  from  which  it  would  have  to  be  ab- 
sorbed by  the  expenditure  of  considerable  work  in  refrigerating. 

Convection.  It  is  by  this  process  that  heat  is  readily  diffused 
through  liquids  and  gases;  for,  when  one  portion  of  the  liquid  is 
heated,  its  density  is  decreased  and  it  is  displaced  by  the  heavier  and 
colder  portions  of  the  liquid,  wrhich  in  turn  are  themselves  displaced 
as  the  heating  process  continues,  until  finally  the  temperature  is 
practically  uniform  throughout.  The  currents  set  up  in  this  process 
of  heating  are  known  as  convection  currents. 

The  same  thing  takes  place  in  the  case  of  heat  applied  to  a  body 
of  gas.  Thus  the  air  in  a  room,  for  example,  being  heated  by  a  stove 
or  other  means,  rises  to  the  ceiling  of  the  room  and  displaces  the 
colder  air,  which,  being  heavier,  falls  to  the  floor  to  be  heated  in  its 
turn.  In  this  case  we  have  convection  air  currents;  and  it  is  owing  to 
currents  of  this  character  that  great  care  must  be  taken  in  construc- 
ting insulating  walls,  where  air  spaces  are  used,  in  such  a  manner 
that  the  spaces  will  be  comparatively  small,  thus  not  allowing  room 
enough  for  the  setting  up  of  such  currents,  which,  if  formed,  would  be 
a  means  of  transferring  heat  to  the  cold  stores  instead  of  acting  as 
an  insulation. 

Neglect  of  this  matter  has  frequently  resulted  in  disappointment 
with  insulation  where  dead  air  spaces  have  been  depended  on  to  a 
considerable  extent.  The  air  in  contact  with  the  warm  wall  on  the 
outside  of  the  chamber  becomes  heated  and  rises  to  the  top  of  the 
space,  whence,  as  it  is  gradually  cooled,  it  falls  down  along  the  com- 
paratively cold  inner  wall,  imparting  its  heat  to  this  wall  during  pas- 
sage. By  the  time  the  air  has  passed  down  this  inner  wall  to  the 
bottom  of  the  space,  it  is  comparatively  cold,  and  then  comes  in  con- 


20  REFRIGERATION 

tact  a  second  time  with  the  outer  wall.  In  this  way  a  continuous 
current  is  set  up,  and  acts  as  a  conveyor  of  heat  from  the  outer  to 
the  inner  wall  of  the  building.  Having  these  facts  in  view,  insulating 
men  have  agreed  that  the  smaller  the  air  space  can  be  made,  the 
deader  it  is;  and  in  modern  work,  this  is  reduced  to  a  nicety  where 
there  are  no  air  spaces  larger  than  the  minute  cells  in  the  structure  of 
cork,  which  is  used  for  insulating  purposes  in  the  best  work  of  the 
present  time. 

Conduction.  This  term  has  reference  to  the  manner  in  which 
heat  is  propagated  through  a  substance,  or  from  one  substance  to 
another  where  the  two  substances  are  in  contact.  Taking  again 
the  case  of  the  iron  bar  heated  at  one  end,  the  molecules  at  the  heated 
end  may  be  considered  as  being  in  a  state  of  violent  agitation  so  that 
each  possesses  a  definite  amount  of  kinetic  (active'or  moving)  energy. 
In  the  cooler  portion  of  the  bar,  the  molecules  will  be  agitated  to  a 
less  extent;  but  those  molecules  in  contact  with  the  similar  molecules 
in  the  hotter  portion  of  the  bar  are  gradually  affected  by  the  impact 
of  these  latter  molecules,  by  which  means  their  rate  of  motion  among 
themselves  is  gradually  increased,  they  receiving  in  the  contact  a 
portion  of  the  energy  of  the  more  violently  agitated  molecules.  In  this 
way  the  heat  energy  of  the  molecules  in  the  cooler  portion  of  the  bar 
is  considerably  increased;  and  the  heat  gradually  passes  thus  from 
molecule  to  molecule  toward  the  cooler  end  of  the  bar,  until  finally 
the  temperature  has  been  made  uniform  throughout  the  entire  length 
of  the  bar  by  the  process  of  conduction. 

PRODUCTION  OF  COLD 

Production  of  cold  is  in  general  effected  by  transfer  of  heat  from 
one  body  or  substance  to  another  at  lower  temperature.  Something 
has  already  been  stated  as  to  the  manner  in  which  heat  transfers 
take  place  and  the  effects  produced  by  such  transfers.  It  remains  to 
be  seen,  then,  how  the  transfers  are  brought  about  in  practice  in  such 
a  way  as  to  give  the  desired  results. 

There  are  three  ways  in  which  heat  transfers  may  be  made  to 
produce  cold,  the  first  of  these  being  by  chemical  action  as  exemplified 
in  the  so-called  freezing  mixtures.  It  has  already  been  seen  that 
when  a  solid  changes  to  the  liquid  form,  the  heat  becomes  latent 
and  the  temperature  correspondingly  lowered,  the  change  being 


REFRIGERATION 


21 


effected  by  separation  of  the  molecules  of  the  substance  in  melting. 
It  is  equally  true  that  the  latent  heat  is  absorbed  when  the  change 
of  state  to  the  liquid  form  is  made  otherwise  than  by  melting,  as  in 
the  case  where  a  solid  is  dissolved  in  water.  Heat,  then,  may  be- 
come latent  with  change  of  state  by  the  process  of  'dissolving  as  well 
as  by  that  of  melting,  the  fall  in  temperature  in  either  case  being 
brought  about  by  the  expenditure  or  exchange  to  the  latent  fofrn  of 
the  heat  energy  necessary  to  separate  the  molecules  of  the  solid  sub- 
stance so  that  it  assumes  the  liquid  form. 

To  illustrate  the  lowering  of  temperature  produced  by  solution, 
take  a  glass  of  water  and  place  in  it  a  thermometer.  On  dissolving 
sugar  or  salt  in  this  water,  the  temperature  will  be  seen  to  fall,  the 
effect  being  much  more  marked  if  the  disolving  process  is  hastened 

TABLE  V 


COMPOSITION  OF  FREEZING  MIXTURES 

RED.  OP  TEMP. 
IN  DEO.   F. 

AMT.  OF 
FALL  IN 
DEO.  F. 

FROM 

To 

Sn 

aw  4  pa 

2 
3 
3 

7    ' 
8 
2 
3 

•ts;  Muriate  of  lime  5  parts 
Common  salt  1  part 
Muriate  of  lime  crys.  3  parts 
Dil.  sulphuric  acid  2  parts 
Hydrochloric  acid  5  parts 
Dil.  nitric  acid  4  parts 
Chloride  of  calcium  5  parts 
crystallized  3  parts 
Potassium  4  parts 

32 
32 
32 
32 
32 
32 
32 
32 
32 

-40 
0 
-50 
-23 
-27 
-30 
-40 
-50 
-51 

72 
32 
82 
55 
59 
62 
72 
82 
83 

by  stirring,  so  that  the  heat  will  not  be  absorbed  from  the  surround- 
ing subjects  before  the  reduction  of  tempeyature  occurs.  One  part 
nitrate  of  ammonia  mixed  with  one  part  of  water  at  50°  F.  gives  a  re- 
duction of  46  degrees,  or  to  4°  F.  Where  two  solids  are  mixed,  one  of 
them  being  at  the  freezing  point,  the  cooling  action  is  still  more  marked. 
Two  parts  of  snow  mixed  with  one  part  of  common  salt  gives  a  reduc- 
tion of  50  degrees;  while  four  parts  of  potash  mixed  with  three  parts 
of  fine  snow  or  crushed  ice  gives  a  drop  from  32°  to  —51°,  or  a  total 
of  83  degrees.  Table  V  gives  the  reduction  in  temperature  for  a 
number  of  other  mixtures,  and  is  of  considerable  value  to  manufac- 
turers of  ice  cream,  in  enabling  them  to  determine  what  materials 
may  be  used  with  greatest  economy  in  freezing  or  packing  cream. 


22  REFRIGERATION 

It  is  in  work  of  this  kind  that  freezing  mixtures  have  their  chief  value, 
the  cooling  produced  being  too  slight  in  proportion  to  the  amount  of 
material  used  to  be  of  any  value  in  producing  refrigeration  on  a  large 
scale  in  commercial  work. 

A  more  practical  and  at  the  same  time  a  rather  expensive  method 
of  producing  refrigeration  for  commercial  purposes,  is  that  in  which 
a  non-condensable  gas  is  expanded  adiabatically,  or  without  the  ad- 
dition or  subtraction  of  heat.  The  gas,  after  being  compressed  and 
cooled,  is  allowed  to  expand  while  doing  work  against  a  piston,  with 
the  result  that  its  temperature  is  lowered.  In  this  machine  the  gas 
is  never  condensed  to  the  liquid  form,  but  merely  compressed  to 
greater  density  than  its  natural  condition.  Air  is  used  in  all  practical 
machines  employing  the  principle  of  adiabatic  expansion;  but  in  no 
case  is  the  air  reduced  to  liquid  form,  as  liquid  air  has  far  too  low  a 
temperature  to  be  of  any  practical  use  for  refrigeration  under  normal 
conditions.  It  is  this  difference  in  handling  the  working  medium  that 
distinguishes  the  compressed-air  machine  from  other  compression 
machines  in  which  the  liquid  is  compressed  and  then  condensed  to 
the  liquid  form  by  cooling. 

The  third  and  most  important  method  of  refrigeration  is  that 
in  which  a  volatile  liquid  is  vaporized  to  absorb  heat,  as  represented 
by  the  latent  heat  of  the  medium  used.  The  heat  of  vaporization 
is  absorbed  from  objects  surrounding  the  working  medium;  and  these 
objects  are  cooled  to  the  temperature  desired,  the  material  used  for 
the  cold  body  in  most  refrigerating  plants  being  a  strong  brine  solu- 
tion. Thus  the  liquid  expanding  in  the  cooling  coils  absorbs  heat 
from  the  brine  in  the  tank  surrounding  these  coils,  and  the  cold  brine 
is  used  to  freeze  ice  or  is  circulated  through  the  cold  storage  rooms, 
the  application  of  the  cold  produced  by  the  expansion  of  the  working 
medium  varying  according  to  the  circumstances  and  requirements 
of  each  case. 

In  the  special  case  of  vaporization  or  latent-heat  machines 
operating  on  what  is  known  as  the  vacuum  system,  water  is  at  once 
the  working  medium  and  the  cold  body,  the  cooling  being  done  by 
evaporating  part  of  a  body  of  water  under  a  vacuum  so  that  the  latent 
heat  taken  up  in  evaporation  reduces  the  temperature  until  the  por- 
tion of  water  remaining  in  the  apparatus  is  frozen.  Owing  to  the 
fact  that  the  latent  heat  of  water  is  large  as  compared  with  other 


REFRIGERATION  23 

liquids  used,  the  freezing  is  very  rapid,  so  that  the  ice  produced  is 
usually  opaque,  there  not  being  time  for  separation  of  the  air  from  the 
water.  It  should  be  noted  that  this  system  depends  for  its  operation 
on  a  vacuum  being  produced,  as  otherwise  the  boiling  point  of  water 
is  at  212°,  which  is  altogether  too  high  a  temperature  for  refrigeration 
work.  The  chief  difficulty,  then,  with  the  vacuum  process,  is  the 
necessity  of  maintaining  the  vacuum,  for  which  complicated  apparatus 
is  required. 

In  the  vacuum  process,  external  energy  is  expended  to  drive  the 
vacuum  pumps  and  other  machinery  connected  therewith;  and  a 
moment's  consideration  will  show  that  in  every  system  external 
energy  is  utilized  at  some  point  in  the  cycle,  thus  obeying  the  thermo- 
dynamic  laws.  It  is  seen  at  once  that  pressure  and  temperature  .tell 
the  w-hole  story  in  refrigerating  \vork,  the  whole  object  of  such  work 
being  the  reduction  of  temperature,  which  reduction  depends  on  the 
pressures  and  corresponding  temperatures  in  the  different  parts  of 
the  system.  As  already  pointed  out,  wrater  cannot  be  used  except  in 
a  vacuum  on  account  of  its  high  temperature  of  vaporization  at 
ordinary  pressures.  Since  it  is  not  desirable  to  operate  with  a 
vacuum  in  all  cases,  other  working  mediums  or  refrigerants  than 
water  must  be  chosen,  and  thus  it  comes  about  that  the  temperature 
at  which  a  substance  will  vaporize  at  a  given  pressure  is  of  first 
importance. 

For  any  given  substance  in  the  form  of  vapor — that  is,  a  fully 
expanded  gas  containing  no  moisture — there  is' a  certain  temperature 
above  which  it  is  impossible  to  liquefy  the  substance  no  matter  how 
great  the  pressure.  This  is  the  critical  temperature.  The  pressure 
that  wTill  cause  liquefaction  at  the  critical  temperature  is  known  as 
the  critical  pressure.  These  twro  critical  points  of  temperature  and 
pressure  determine  largely  whether  or  not  a  given  substance  is  suit- 
able as  the  working  medium  in  refrigerating  machines.  Aside  from 
its  latent  heat,  which  should  preferably  be  high,  the  substance  should 
have  such  critical  data  as  to  make  it  possible  to  work  it  in  the  refriger- 
ating machine  at  ordinary  pressures  and  temperatures,  for  otherwise 
the  special  apparatus  required  to  manipulate  it  will  be  too  expensive 
to  be  practical.  Table  VI  gives  the  critical  pressure  and  temperature, 
with  the  corresponding  density,  for  a  number  of  substances.  It  is 
seen  that  ammonia,  carbon  dioxide,  and  sulphur  dioxide  are  the  only 


24 


REFRIGERATION 


three  substances  that  have  the  critical  points  at  anything  like  normal 
conditions  of  temperature  and  pressure.  Hence  the  choice  of  a  re- 
frigerant from  among  the  many  volatile  liquids  known  to  chemistry 
is  narrowed  down  to  these  three  substances. 

There  is  considerable  discussion  and  expression  of  opinion  among 
engineers  as  to  which  of  these  three  is  best.  Generally  speaking, 
the  choice  of  any  substance  from  an  engineering  standpoint  depends 
on  the  latent  heat  of  the  liquid  per  pound ;  the  boiling  point  at  ordi- 
nary pressures;  the  number  of  cubic  feet  that  must  be  compressed 

TABLE  VI 
Critical  Data 


H  ° 

Kb 

S.s 

w 

£  i  fa 

»  g  Hfe 

*  w  " 

1  "t^ 

P    i-3 

-°K  K  H 

CL  M  ^  a 

^  ^  s 

w  ^  ' 

o     rt 

SUBSTANCE 

PH  a.  p  g) 
°ogg 

IfiS 

JI« 

8  fl 

mi 

ffH       5 

K  H       * 

IS(2 

s^§ 

^g 
55-5 

j  jj 

O     rt 

Water                                               H2O 

+  212 

+    32 

+  657 

205 

0  037 

Alcohol  C2H60 

+  172 

-148 

+  423 

67 

0.114 

Sulphur  dioxide  SO2 

-    14 

-105 

+  313 

81 

Ammonia  NH3 

-   27.4 

-106.6 

+  266 

115 

0.048 

Carbonic  acid  (carbon  dioxide)  .  .  .  CO2 
Oxygen  O 

-110 
-296 

-110 
-269 

+   88 
-180 

75 
52 

0.035 

Atmospheric  air  

-312 

-220 

39 

Nitrogen  N 

-317 

-353 

-231 

36 

-400 

-382 
-231  9 

21 
45 

0.037 

Air  ... 

Nitrous  oxide 

+   96 

75 

to  produce  a  certain  refrigerating  effect  (or,  in  other  words,  the  size 
of  the  compressor  necessary);  the  pressure  required  to  produce  lique- 
faction of  the  gas  at  certain  temperatures ;  and  the  specific  heat  of  the 
liquid.  Table  VII  gives  the  boiling  point  and  latent  heat  of  a  number 
of  substances  at  14.7  pounds,  and  also  gives  the  specific  heat  of  the 
liquids  used  in  refrigerating  work. 

Under  atmo'spheric  pressure,  carbon  dioxide  boils  at  —110°  F., 
or  far  below  the  temperatures  required  in  ordinary  refrigerating  work. 
By  reference  to  Table  VI,  it  is  seen  that  this  refrigerant  must  be  lique- 
fied under  about  900  pounds  pressure,  and  in  view  of  this  it  would 
seem  advisable  to  carry  a  higher  pressure  on  the  suction  line  to  the 
compressor  than  is  carried  with  the  machines  using  the  other  refriger- 


REFRIGERATION 


25 


ants,  which  are  liquefied  at  lower  condensing  pressures.  With  a 
pressure  of  342  pounds  a  square  inch,  carbon  dioxide  toils  with  a 
temperature  of  5°  F.,  its  latent  heat  under  these  conditions  being 
121.5  B.  T.  U.  This  temperature  is  about  as  low  as  is  usually  re- 
quire:! in  refrigerating  work,  and  gives,  thererore,  an  index  of  the 
suction  pressure  that  may  be  carried. 

Passing  by,  then,  those  refrigerating  agents  that  have  been  tried 
and  found  wanting,  such  as  the  various  forms  of  ether  and  its  com- 

TABLE  VII 
Boiling  Point  and  Latent  Heat  of  Substances 


SUBSTANCE 

TEMPEHA- 

TURE    OF 

BOILING 

POINT 

LATENT 
HEAT 
B.  T.   U. 

SPECIFIC 
HEAT  OP 
LIQUID 

Nitric  acid  
Saturated  brine  

248°  P. 
220°  F. 

Water  
Alcohol  
Chloroform  
Ether,  sulphurous  
Ether,  methyl  
Sulphur  dioxide  
Anhydrous  ammonia  
Carbon  dioxide  

212°  F. 
173°  F. 
140°  F. 
95°  F. 
-10°  F. 
14°  F. 
-28.  5°  F. 
-110°  F. 

966 
i70 

ies.7 

573 

141 

1  .0000 

.5299 

'  .4100 
1  .0058 
.9550 

binations  with  sulphur  dioxide;  and  also  such  agents  as  cryogene, 
acetylene,  naphtha,  and  gasoline,  it  will  be  sufficient  to  give  in  some 
detail  the  properties  of  sulphur  dioxide,  carbon  dioxide,  and  am- 
monia, which  are  in  common  use  as  refrigerants.  Table  VIII 
gives  the  qualities  of  these  three  refrigerants,  and  should  be  given 
careful  study,  as  it  shows  up  the  good  and  bad  points  of  each  refrig- 
erant in  the  clearest  manner.  It  will  be  seen  in  the  column  next  to 
the  last,  that  the  size  of  the  sulphur  dioxide  compressor  is  about 
twenty  times  that  of  the  carbon  dioxide  machine,  or  three  times 
as  large  as  the  ammonia  machine,  which  itself  is  something  like 
five  times  the  size  of  the  carbon  dioxide  machine.  The  size  of 
machine,  of  course,  determines  to  a  large  extent  the  amount  of  fric- 
tion losses.  Other  things  being  equal,  the  smaller  the  machine,  the 
better. 

The  great  disadvantages  of  the  carbon  dioxide  machine  are  the 
high  pressures  required  and  the  comparatively  high  specific  heat  of 
the  liquid,  which  means  that  considerable  of  the  cooling  effect  pro- 


26 


UEFRIGERATION 


J 

>    « 

w  3 

-    ~ 

<I 

•5 

i 


•XN30  H3d  'aiaoiT  oNnooa  ox  SHQ  S8<yl 

r-l    •*    00 
00    <N    rH 

O   O   O 

NOIXVH3DIH.J3H    IVQOg 
HOJ  HO883HdWOQ  JO  3  WmO  A  3AIXV13^J 

s;^^ 

"S§5 

(-X3Xg)    SOVHVaq    QNV    'NOIX 

a  co  <M 

r-l     Tjl     Tfl 

(cnajaxaxg) 
'il  o^I  tv  'arl  aad  '&JL  'nO  KI  awmoV 

••t1    CO   O 
O    1C    !>• 

(Q13J3X3ig  'ZM3HO--[)  3WQ1OA  'HdWOO 

•xj  -a^Had  "ziHOdVA^o  xvajj  a'fljaefj 

O   OO   O 

O    C^    GO 

1C 

amOr^aHx  DNnooQ  ox  aaQ  %  NI  ssoq 

j>     1C     Tf 

(aiajaxaxg)  -,j  Of-i  xv 

•XJ    -aQ    H3d    NOIXVZIHOdVA   ^O    XV3JJ 

co  c^  co 

00    CO    GO 

(VXVQ  01Q) 

•xj  -aQ  aad  NoixvziHOdVA  -*o  xvajj    • 

i>  co  t» 

•*    <N    <O 

(ai3J3X3xg   'zNsaoq  'asn 

C>    t^    1C 
t^     IM     rH 

0     0     rH 

(VXVQ     Q1Q) 
QIQbiq  3HX  JO  XV3JJ   .il   1  1    i  1.  Iv; 

!"•§ 

(aiaj3xaxg   'ZNanoq) 
'>!  oO  -iv  -aq  H3d  -x^  -03  NI  swmoA 

co  -^  ic 
0  t-  OS 

(VXVQ  QiQ)   'J  oO  iv 
annoj  Had  xas^  oiaa^  NI  awmoA 

t^   iC   O 

(N     CO     rH 

0   t-'   Os' 

(ZN3HOq)    -J    0Q  XV 

rH     rH     1C 

(VXVQ  aiQ)  'J  00  iv 

(N    d    "3 

a   aoj            NOIX  zi          A  *      *      « 

'iJ    oO    iV    HONJ 

•ftg  H3d  'saq  NI  aanesaaj  axaiosay 

000 

rnrHCO 

•'           1 

•   oo 

Carbon  dioxide  CO2 
Sulphur  dioxide  SO2 
Ammonia  NH3 

REFRIGERATION 


27 


duced  by  evaporation  will  be  absorbed  in  reducing  the  temperature 
of  the  liquid  from  that  of  the  condenser  to  that  in  the  expansion  coils 
or  cooler.  This  is  shown  up  clearly  in  the  last  column  of  the  table, 
where  it  is  seen  that  the  loss  due  to  cooling  the  liquid— as  shown  in 
percentage  for  every  degree  difference  of  temperature  between  the 
condenser  and  cooler — is  less  for  ammonia  than  for  any  other  liquid, 
the  loss  being  high  with  carbonic  acid.  The  chief  point  in  favor  of 
sulphur  dioxide  or  sulphuric  acid  is  the  low  pressure  of  its  vapor, 
but  the  large  size  of  machine  required  for  this  refrigerant  has  pre- 
vented its  coming  into  general  use. 

Table  IX  gives  the  comparative  refrigerating  values  of  the 
refrigerants  most  in  use,  and  shows  at  a  glance  the  standing  of  each 
on  the  principal  scores  of  value. 

TABLE  IX 
Comparative  Values  of  Three  Refrigerants 


g. 

, 

K 

0 

^ 

B 

W 

OH 

K 

P  P 

",- 

^ 

H 

. 

o| 

a 

PU 

11 

H 

& 

|- 

s3( 

W 

g2 

ice 

S5  H 

& 

?  « 

,8$ 

6» 

sz 

ij  z 

0     ' 

w 

i! 

22 

tf 

z  ;> 

, 

2 

oli 

PfH[^ 

• 

ftp 

•     SUBSTANCE 

K  H 

04    CU 

-  2 

V    ^ 

W 

O 

d  ^ 

T> 

I 

1 

S2 

^gP 

SH 

s^ 

o  o 

i-j 

p*  P« 

o  • 

^H 

j  tf 
<  a 

U  B. 

H  K 

H 

W 
p 

Q 

SSj3 

?:  " 

H 
O 
H 

II 

«g 

?*•  o  M 

§e 

U 
B 

E« 

h 
W 

J 

H^rJ 

P  O 

J  w 

CO   tf 

w 

^ 

Ko 

as 

1 

tar 

Q 

P    • 

E^ 

1 

i 

i 

f< 

! 

1 

1 

^2 

I5 

a 

-< 

PH 

Carbon  dioxide  CO2 

0.49 

6 

5 

4 

9 

24 

0.60 

0.61 

14,855 

13,370 

Sulphur  dioxide  ....  SO, 
Ammonia  NH3 

7.04 
2.4 

6 
6 

6 
6 

14 

11 

25 

49 
48 

10.556 
3.56 

10.6 
4.00 

16,673 
16,673 

13,300 
13,300 

In  case  of  the  carbon  dioxide  machine,  particular  attention 
should  be  given  to  the  temperature  of  the  cooling  water,  as  the  critical 
temperature  of  this  refrigerant  is  not  much  above  the  ordinary  sum- 
mer temperature  of  river  water  from  natural  sources  of  supply. 
Where  the  initial  temperature  at  the  condensers  is  70°  or  more,  it  is 
advisable  to  increase  the  supply  of  cooling  water  so  as  to  maintain 
an  average  condenser  temperature  of  75°.  With  temperatures  greater 


28  REFRIGERATION 

than  this,  the  efficiency  of  the  carbon  dioxide  machine  falls  off  as 
compared  with  the  other  two  systems,  but  even  with  water  at  90 
degrees,  the  machine  will  develop  about  70  per  cent  of  its  normal 
capacity.  Theoretically  the  efficiency  of  the  carbon  dioxide  machine 
is  about  12  per  cent  less  than  that  of  the  ammonia  and  sulphur 
dioxide  machines,  but  practical  compensating  features  enable  the 
machine  to  make  up  for  this.  Stetfeld  has  found  that  the  losses 
resulting  from  radiation  in  the  clearance  spaces  of  the  refrigerator, 
the  resistance  of  the  gases  on  their  way  from  the  refrigerator  to  the 
compressor  and  in  passing  the  suction  valve,  and  friction  and  valve 
leakage,  all  together,  average  49  per  cent  of  the  losses  in  the  ammonia 
and  sulphur  dioxide  systems,  and  not  more  than  25  per  cent  when 
carbon  dioxide  is  used. 

With  the  carbon  dioxide  machine,  for  example,  the  piston  leak- 
age averages  about  9  per  cent,  as  against  25  per  cent  in  the  ammonia 
and  sulphur  dioxide  machines.  In  carbon  dioxide  machines,  the 
great  density  of  the  gas  permits  making  the  valves,  passages,  and 
suction  pipes  large  enough  to  materially  reduce  frictional  losses, 
and  yet  not  so  large  as  is  necessary  in  the  other  machines.  In  view  of 
these  facts,  engineers  have  generally  concluded  that  the  practical 
efficiency  of  the  three  refrigerants  mainly  employed  is  about  equal 
when  each  is  used  to  best  advantage.  This  is  shown  in  the  last  column 
of  Table  IX.  The  choice  therefore  depends  on  circumstances  and 
the  local  conditions  in  any  case.  To  determine  the  fitness  of  the 
refrigerant  for  any  set  of  conditions,  its  natural  characteristics  must 
be  taken  into  consideration. 

While  ammonia  and  sulphur  dioxide  have  a  sharp  penetrating 
odor,  carbon  dioxide  is  odorless;  and  if  leaks  are  to  be  detected 
readily,  the  charge  must  be  made  odoriferous  by  adding  a  small 
amount  of  alcohol  impregnated  with  camphor.  At  high  tempera- 
tures, ammonia  dissociates  into  its  constituent  gases  and  loses  its 
value  as  a  refrigerant,  while  the  gases  formed  have  a  detrimental 
effect  on  the  working  of  the  machine.  It  is  not  definitely  settled  as 
to  the  exact  temperature  at  which  this  dissociation  takes  place;  but 
it  is  certain  that  above  900°  F.,  ammonia  gas  is  gradually  decomposed, 
until  at  about  ]  ,600°,  complete  dissociation  takes  place.  It  is  believed 
that  the  action  goes  on  to  some  extent  at  lower  temperatures,  but  just 
under  what  conditions  and  to  what  extent  are  not  definitely  known. 


REFRIGERATION  29 

Carbon  dioxide  does  not  decompose  under  any  conditions,  and  is  a 
fire  extinguisher,  while  ammonia  mixed  with  lubricating  materials, 
etc.,  may  support  combustion  in  case  of  an  explosion.  Ammonia 
to  some  extent,  and  sulphur  dioxide  particularly,  have  a  corrosive 
effect  on  metals,  and  the  machines  must  be  designed  with  this  in  view, 
a  special  close-grained  steel  cylinder  being  used  in  ammonia  com- 
pressors of  the  best  manufacture.  Carbon  dioxide  is  entirely  neutral 
in  its  action  on  metals,  and  in  the  event  of  accidents  resulting  in  large 
leaks,  it  has  a  marked  advantage,  as  8  per  cent  of  the  gas  in  the  air 
can  be  inhaled  with  safety  while  less  than  1  per  cent  of  ammonia  gas 
is  dangerous  to  life.  Large  losses  have  frequently  resulted  by 
damage  to  goods  in  store  where  ammonia  has  escaped,  but  this  can- 
not happen  where  carbon  dioxide  machines  are  employed,  as  the 
gas  does  no  damage. 

Sulphur  dioxide  was  used  as  a  refrigerant  in  the  early  stages  of 
modern  machine  development  after  the  ether  machine  had  its  day. 
Owing  to  the  high  cost  of  ether,  and  other  disadvantages  connected 
with  its  use — principally  its  inflammability — investigators  took  up 
sulphur  dioxide  and  studied  its  properties  as  a  refrigerant.  It  was 
found  to  require  a  higher  condensing  pressure  than  ether,  but  did 
not  need  to  be  evaporated  under  a  vacuum,  so  that  the  compressor 
could  be  made  smaller  for  a  given  capacity.  On  account  of  the 
higher  condensing  pressure,  it  was  necessary  to  build  the  compressor 
stronger  than  had  formerly  been  done,  and  more  attention  was  given 
to  the  elimination  of  clearance  spaces.  Even  though  the  machine 
for  use  with  this  refrigerant  is  smaller  than  that  formerly  used  with 
ether  as  a  refrigerant,  it  is  still  much  larger  than  ammonia  and  carbon 
dioxide  machines,  as  has  been  shown  in  the  tables.  Table  X  gives 
the  properties  of  sulphur  dioxide. 

Carbon  dioxide,  although  not  used  extensively  until  within  a 
comparatively  recent  period,  is  coming  into  favor,  for  it  is  made  as  a 
by-product  in  certain  industries  and  can  be  obtained  cheaply.  The 
gas  is  not  readily  absorbed  by  water  or  by  lubricating  materials; 
and,  not  being  easily  dissociated,  the  system  using  it  remains  free  of 
non-condensable  gases  and  in  efficient  condition.  Table  XI  gives 
the  properties  of  this  refrigerant. 

Ammonia,  the  most  widely  used  of  all  refrigerants,  is  composed 
of  one  part  of  nitrogen  in  combination  with  three  of  hydrogen,  this 


30 


REFRIGERATION 


TABLE  X 
Properties  of  Saturated  Sulphur  Dioxide 


TEMPERA- 
TURE  OF 
EBULLITION 
IN  DEO.  F. 

ABSOLUTE 
PRESSURE 

IN    I.  US. 

PER  SQ.  IN. 

TOTAL  HEAT 
RECKONED 

FROM    32° 

FAHR. 

HEAT  OF 
LIQUID 
RECKONED 

FROM   32° 

FAHR. 

LATENT 
HEAT  OF 
VAPORIZA- 
TION 

DENSITY 
OF  VAPOR. 
OR  WEIGHT 

OF    1 

CUBIC  FT. 

DEO.  F. 

LBS. 

B.  T.  U. 

B.  T.  U. 

B.  T.  U. 

LBS. 

-40 

3.16 

155.22 

-17.76 

172.98 

.048 

-31 

4.23 

156.39 

-16.55 

172.94 

.062 

-22 

5.56 

157.55 

-15.05 

172.60 

.079 

-13 

7.23 

158.69 

-13.26 

171.95 

.099 

-  4 

9.27 

159.82 

-11.18 

171.00 

.124 

5 

11.76 

160.93 

-  8.82 

169.75 

.154 

14 

14.75 

162.02 

-  6.17 

168.19 

.190 

23 

18.31 

163  .  10 

-  3.23 

166.33 

.232 

32 

22.53 

164.16 

0.00 

164.16 

.282 

41 

27.48 

165.21 

3.52 

161.69 

.341 

50 

33.26 

166.24 

7.32 

158.92 

.410 

59 

39.93 

167.25 

11.41 

155.84 

.491 

68 

47.62 

168.25 

15.79 

152.46 

.584 

77. 

56.39 

169.23 

20.45 

148  .  78 

.692 

86 

66.37 

170.20 

25.41 

144.79 

.819 

95 

77.64 

171.15 

30.65 

140.50 

.965 

104 

90.32 

172.08 

36.18 

135.90 

1.131 

TABLE  XI 
Properties  of  Saturated  Carbon  Dioxide 


TEMPER- 
ATURE OP 
EBULLITION 
IN  DEO.  F. 

ABSOLUTE 
PRESSURE 
IN   LBS. 
PER  SQ.  IN. 

TOTAL  HEAT 

FROM   32°   F. 

HEAT  OF 
LIQUID 

FROM   32°    F. 

LATENT  HEAT 
OF  VAPORIZA- 
TION 

DENSITY  OF 
VAPOR,  OR 
WEIGHT  OF 
1  Cu.  FT. 

-22 

210 

98.35 

-37.80 

136.15 

2.321 

-13 

249 

99.14 

-32.51 

131.65 

2.759 

-  4 

292 

99.88 

-26.91 

126.79 

3  265 

5 

342 

100  .  58 

-20.92 

121.50 

3.853 

14 

396 

101.21 

-14.49 

115.70 

4.535 

23 

457 

101  .81 

-  7.56 

109.37 

5.331 

32 

525 

102.35 

0.60 

102.35 

6.265 

41 

599 

102.84 

8.32 

94.52 

7.374 

50 

680 

103.24 

17.60 

85.64 

8.708 

59 

768 

103.59 

28.22 

75.37 

10.356 

68 

864 

103.84 

40.86 

62.98 

12.480 

77 

968 

103.95 

57.06 

46.89 

15.475 

86 

1,080 

103  .  72 

84.44 

19.28 

21.519 

being  the  only  proportion  in  which  these  two  gases  combine.  Anhy- 
drous ammonia  thus  formed,  when  dissolved  in  water,  gives  the  aqua 
ammonia  of  commerce,  used  in  absorption  machines.  When  heat 
is  applied  to  this  aqua  ammonia  in  the  generator  of  the  absorption 


REFRIGERATION 


31 


TABLE  XII 
Properties  of  Saturated  Ammonia  Gas 

DE  VOLSON  WOOD  AND  GEO.  DAVIDSON 


M 

,     M 

*    8 

~ 

*8 

o 

1.8 

*  OJ  ffi 

i«S 

W 

H 

®  ^  £ 

M 

°z 

P& 

o£ 

£mm 

II: 

rJ 

IPERATUR 

:OREES  F. 

||| 

III 

B.  H 

§§g 

s«s* 

ooS 

)LUME  OF 
ND  OFLlQ 

!UBIC  FEI 

S»H  0 

:§!.< 

1*5 

wSa 

ill 

O  OS32 

EHQ 

^|o 

H!»  B 

>l& 

££2 

w  pw 

•*-! 

C5 

<J  fc 

ij     fc 

"V 

-1" 

-4.01 

10.69 

-40 

420.66 

579.67 

24.38 

.0410 

.0234 

42.589 

-2.39 

12.31 

-35 

425.66 

576.68 

21.32 

.0469 

.0236 

42.337 

-0.57 

14.13 

-30 

430.66 

573.69 

18.69 

.0535 

.0237 

42  .  123 

1.47 

16.17 

-25 

435.66 

570.68 

16.44 

.0608 

.0238 

41.858 

3.75 

18.45 

-20 

440.66 

567.67 

14.51 

.0690 

.0240 

41.615 

6.29 

20.99 

-15 

445.66 

564.64 

12.83 

.0779 

.0241 

41.374 

9.10 

23.80 

-10 

450.66 

561.61 

11.38 

.0878 

.0243 

41.135 

12.22 

26.92 

-  5 

455.66 

558.56 

10.12 

.0988 

.0244 

40.900 

15.67 

30.37 

0 

460.66 

555.50 

9.03 

.1167 

.0246 

40.650 

19.46 

34.16 

5 

465.66 

552.43 

8.07 

.1240 

.0247 

40.404 

23.64 

38.34 

10 

470.66 

549.35 

7.23 

.1383 

.0249 

40.160 

28.24 

42.94 

15 

475.66 

546.26 

6.49 

.1541 

.0250 

39.920 

33.25 

47.95 

20 

480.66 

543.15 

5.84 

.1711 

.0252 

39.682 

38.73 

53.43 

25 

485.66 

540.03 

5.27 

.1897 

.0253 

39.432 

44.72 

59.42 

30 

490.66 

536.91 

4.76 

.2099 

.0255 

39.200 

51.22 

65.92 

35 

495.66 

533.78 

4.31 

.2318 

.0256 

38.940 

58.29 

72.99 

40 

500.86 

530.63 

3.91 

.2554 

.0258 

38.684 

65.96 

80.66 

45 

505.66 

527.47 

3.56 

.2809 

.0260 

38.461 

74.26 

88.96 

50 

510.66 

524.30 

3/24 

.3084 

.0261 

38.226 

83.22 

97.92 

55 

515.66 

521.12 

2.96 

.3380 

.0263 

37.994 

92.89 

107.59 

60 

520.66 

517.93 

2.70 

.3697 

.0265 

37.736 

103.33 

118.03 

65 

525.66 

514.73 

2.48 

.4039 

.0266 

37.481 

114.49 

129.19 

70 

530  66 

511.52 

2.27 

.4401 

.0268 

37.230 

126.52 

141.22 

75 

535.66 

508.29 

2.09 

.4791 

.0270 

86.995 

139.40 

154.10 

80 

540.66 

505.05 

1.92 

.5205 

.0272 

36.751 

153.18 

167.88 

85 

545.66 

501.81 

1.77 

.5649 

.0273 

36.509 

167.92 

182.62 

90 

550.66 

498.55 

1.64 

.6120 

.0275 

36.258 

183.65 

198.35 

95 

555.66 

495.29 

1.51 

.6622 

.0277 

36.023 

200.42 

215.12 

100 

560.66 

492.01 

1.39 

.7153 

.0279 

35.778 

218.28 

232.98 

105 

565  .  66 

488.72 

1.289 

.7757 

.0281 

237.27 

251.97 

110 

570  .  66 

485.42 

1.203 

.8312 

.0283 

258.7 

272.14 

115 

575.66 

482.41 

1.121 

.8912 

.0285 

275.79 

293.49 

120 

580.66 

478.79 

1.041 

.9608 

.0287 

301.46 

316.16 

125 

585.66 

475.45 

.9699 

1.0310 

.0289 

325  .  72 

340.42 

130 

590.66 

472.11 

.9051 

1  .  1048 

.0291 

350.46 

365.16 

135 

595.66 

468.75 

.8457 

1  .  1824 

.0293 

377.52 

392.22 

140 

600.66 

465.39 

.7910 

1.2642 

.0295 

405  .  79 

420.49 

145 

605.66 

462.01 

.7408 

1.3497 

.0297 

435.5 

450.20 

150 

610.66 

458.62 

.6946 

1.4396 

.0299 

466.84 

481.54 

155 

615.66 

455.22 

.6511 

1.5358 

.0302 

499  .  70 

514.50 

160 

620.66 

451.81 

.6128 

1.6318 

.0304 

534.34 

549.04 

165 

625.66 

448.39 

.5765 

1.7344 

.0306 

One  atmosphere  in  this  table  is  equal  to  a  pressure  of  a  column  of  mercury  29.9  in.  high 
Specific  heat  of  ammonia  gas  and  vapor  at  constant  pressure.  =  0.508 

The  same  at  constant  volume =   0.3913 

Weight  of  I  cubic  foot  liquid  ammonia  at  32  degrees  F =39.108  pounds 

Volume  of  1  pound  liquid  ammonia  at  32  degrees  F =  0.02557  cubic  feet 

Specific  heat  of  liquid  ammonia =  1.01235  +  0.008378  t« 


32 


REFRIGERATION 


machine,  the  gas  is  distilled  off,  because  it  evaporates  at  a  lower  tem- 
perature than  the  water;  and,  when  freed  from  all  moisture  in  the  an- 
alyzer and  rectifier,  the  gas  is  again  in  the  anhydrous  form.  This  anhy- 
drous gas,  when  liquefied  by  cooling  under  pressure  and  allowed  to 
evaporate  at  atmospheric  pressure,  has  a  temperature  of  —  £8.5°. 
When  subjected  to  a  temperature  of  —94°  F.,  the  liquid  anhydrous 
ammonia  freezes  solid.  Table  XII  gives  some  of  the  properties  cf 
ammonia. 

Aqua  ammonia,  or  ammonia  liquor,  is  the  ordinary  ammonia 
known  to  commerce,  as  distinguished  from  anhydrous  ammonia 
either  in  the  form  of  gas  or  as  liquid.  It  is  nothing  more  than  a 
solution  of  the  anhydrous  gas  in  water.  At  32°  F.  and  atmospheric 
pressure,  water  absorbs  1,140  times  its  volume  of  ammonia  gas,  and 
the  amount  of  the  gas  that  can  be  absorbed  under  other  conditions 
is  governed  by  the  temperature  of  the  water  and  the  pressure  of  the 
gas,  as  shown  in  Table  XIII. 

TABLE  XIII 
Solubility  of  Ammonia  in  Water 

SIMS 


ABSOLUTE 
PRESSURE 

32< 

F. 

68° 

F. 

104 

3  F. 

212C 

F. 

IN  LBS.  PER 
SQ.  IN. 

LBS. 

VOLS. 

LBS. 

VOLS. 

LBS. 

VOLS. 

GRAMS 

VOLS. 

14.67 

0.899 

1.180 

0.518 

.683 

0.338 

.443 

0.074 

.970 

15.44 

0.937 

1.231 

0.535 

.703 

0.349 

.458 

0.078 

.102 

16.41 

0.980 

1.287 

0.556 

.730 

0.363 

.476 

0.083 

.109 

17.37 

1.023 

.351 

0.574 

.754 

0.378 

.496 

0.088 

.115 

18.34 

1.077 

.414 

0.594 

.781 

0.391 

.513 

0.092 

.120 

19.30 

1.126 

.478 

0.613 

.805 

0.404 

.531 

0.096 

.126 

20.27 

1.177 

.546 

0.632 

.830 

0.414 

.543 

0.101 

.132 

21.23 

1.236 

.615 

0.651 

.855 

0.425 

.558 

0  .  106 

.139 

22.19 

1.283 

.685 

O.GG9 

.878 

0.434 

.570 

0.110 

.140 

22.16 

1.336 

.751 

0.685 

.894 

0.445 

.584 

0.115 

.151 

24.13 

1.388 

.823 

0.704 

.924 

0.454 

.596 

0.120 

.157 

25.09 

1.442 

.894 

0.722 

.948 

0.463 

.609 

0.125 

.164 

26.06 

1.496 

.965 

0.741 

.973 

0.472 

.619 

0.130 

.170 

27.02 

1.549 

2.034 

0.761 

.999 

0.479 

.629 

0.135 

.177 

27.99 

1.603 

2.105 

0.780 

1.023 

0.486 

.628 

28.95 

1.656 

2.175 

0.801 

1  .052 

0.493 

.647 

30.88 

1.758 

2.309 

0.842 

1.106 

0.511 

.671 

32.81 

1.861 

2.444 

0.881 

1.157 

0.530 

.606 

34.74 

1.966 

2.582 

0.919 

1.207 

0.547 

.718 

36.67 

2.020 

2.718 

0.955 

1.254 

0.565 

.742 

38.60 

0.992 

1.302 

0.579 

.764 

40.53 

0.594 

.780 

REFRIGERATION  33 

As  gas  is  absorbed  in  the  water,  its  density  changes,  the  solution 
being  lighter  than  water  or  of  less  specific  gravity,  and  it  is  this  fact 
that  affords  means  of  measuring  the  density  of  aqua  ammonia.  Such 
measurements  are  made  by  an  instrument  called  a  hydrometer,  which 
consists  of  a  mercury  tube  having  a  bulb  near  the  middle  and  a 
second  bulb  at  the  lower  end,  the  first  bulb  serving  to  give  the  instru- 
ment buoyancy,  while  the  one  at  the  bottom,  which  is  partially  filled 
with  mercury,  gives  balance  and  holds  the  tube  vertical.  Fig.  1 
shows  the  instrument  in  use  in  a  vessel  of  liquid  the  density  of  which 
it  is  desired  to  ascertain. 

As  seen  in  the  illustration,  the  upper  part 
of  the  tube  is  graduated,  the  ordinary  method 
of  graduating  being  that  devised  by  Baume", 
in  which  the  point  on  the  tube  at  the  surface  of 
a  liquid  composed  of  10  parts  salt  and  90  parts 
water  is  marked  "0,"  and  the  point  to  which 
the  tube  sinks  when  put  in  pure  distilled  water 
is  marked  "10"  degrees.  The  space  between 
the  two  fixed  points  thus  determined  is  di- 
vided into  ten  parts,  and  the  graduations  are 
continued  to  the  top  of  the  tube  or  stem.  In 
another  method  of  graduating,  the  reading  for 
distilled  water  is  marked  "0"  instead  of  "10" 
degrees,  but  this  instrument  is  not  used  ex- 
tensively. To  avoid  calculation  in  using  the 
hydrometer,  it  is  convenient  to  use  the  data 
given  in  Table  XIV,  which  shows  the  number  l  H  drometer 

of  parts  of  ammonia  gas  in  100  parts  of  the  in  ^se- 

solution,  and  the  specific  gravity  of  the  liquid,  as  well  as  the  hydrom- 
eter reading  corresponding  thereto. 

Tests  of  Refrigerants.  Sulphuric  acid  or  sulphur  dioxide  is 
not  used  to  any  extent  at  the  present  time;  but  where  used,  the  only 
tests  to  be  made  are  for  chemical  purity,  and  these  are  best  made  by 
a  chemist.  Carbon  dioxide  is  ordinarily  contaminated  by  air,  car- 
bon bisulphide,  hydrocarbons,  water,  and  oil  or  grease,  all  of  which 
should  be  eliminated  as  far  as  possible.  The  chief  trouble  caused 
by  water  is  due  to  its  tendency  to  freeze  and  clog  the  system  with 
icicles  that  interfere  with  the  circulation  of  the  gas.  Its  presence 


34 


REFRIGERATION 


may  be  detected  by  a  test  made  with  a  piece  of  filter  paper  which  is 
prepared  by  soaking  in  a  solution  of  copper  sulphate  and  drying 
thoroughly,  when  it  has  a  slightly  greenish  color.  The  test  is  per- 
formed by  holding  the  paper  in  a  blast  of  the  carbon  dioxide  allowed 
to  escape  from  a  drum  by  opening  a  valve,  this  being  done  before  the 
refrigerant  is  charged  into  the  system.  If  the  color  of  the  paper 
changes  to  blue,  it  is  evidence  of  too  much  moisture  in  the  gas;  and 
to  get  rid  of  the  water,  the  drum  is  turned  upside  down,  when  the 
water  will  settle  to  the  bottom  of  the  drum,  underneath  the  carbon 
dioxide,  and  may  be  drained  off  by  opening  the  valve, 

TABLE  XIV 
Strength  of  Aqua  Ammonia 


PERCENTAGE  or 

DBOREEf 

s  BAUME 

WEIGHT 

Water  10° 

Water  0° 

0 

1.000 

10.0 

0 

1 

.993 

11.0 

1.0 

2 

.986 

12  0 

2.0 

4 

.979 

13.0 

3.0 

6 

.972 

14.0 

4.0 

8 

.966 

15.0  ' 

5.0 

10 

.960 

16.0 

6.0 

"12 

.953 

17.1 

7.0 

14 

.945 

18.3 

8.2 

16 

.938 

19.5 

9.2 

18 

.931 

20.7 

10.3 

20 

.925 

21.7 

11.2 

22 

.919 

22.8 

12.3 

24 

.913 

23.9 

13.2 

26 

.  .907 

24.8 

14.3 

28 

.902 

25.7 

15.2 

30 

.897          » 

26.6 

16.2 

32 

.892 

27.5 

17.3 

34 

.888 

28.4 

18.2 

36 

.884 

29.3 

19.1 

38 

.880 

30.2 

20.0 

Where  water  is  present  in  the  piping  and  connections  of  a  machine 
using  carbon  dioxide,  it  will  gradually  work  into  the  suction  line  at 
the  compressor;  and  when  the  machine  is  shut  down,  the  water  may 
be  drawn  off,  care  being  taken  to  disconnect  the  expansion  coils  and 
the  suction  line  before  opening  the  drain-cock  on  the  line  at  the  com- 
pressor. As  a  rule,  there  is  not  enough  oil  in  carbon  dioxide  to  cause 
trouble,  but  care  should  be  taken  not  to  allow  the  lubricating  material 
to  foul  the  pipes  and  connections. 


REFRIGERATION  35 

Non-condensable  gases  give  the  most  trouble,  and  should  never 
be  allowed  in  the  system  in  excess  of  3  per  cent.  A  test  for  such  gases 
is  performed  by  drawing  a  given  quantity  of  the  refrigerant  into  a 
clean  glass  tube,  and  absorbing  the  carbon  dioxide  gas  with  caustic 
potash  shaken  up  in  the  tube  while  the  end  is  closed  with  the  finger. 
As  absorption  goes  on,  more  alkali  is  added  by  dipping  the  mouth  of 
the  tube  into  the  potash  solution,  and  when  absorption  ceases,  the 
permanent  gases  remaining  may  be  compared  with  the  quantity  of 
the  refrigerant  drawn  off.  If  air  and  other  gases  are  shown  in  excess 
of  3  per  cent  by  this  test,  the  drum  containing  carbon  dioxide  should 
be  set  upright  and  the  gas  vented  off  until  a  second  sample  taken 
meets  the  test. 

Ammonia  Test.  In  discussing  aqua  ammonia,  the  method  of 
testing  its  density  by  the  hydrometer  has  been  explained  in  detail. 
So  long  as  such  ammonia  is  of  the  desired  density  and  is  composed 
of  pure  anhydrous  ammonia  absorbed  in  reasonably  pure  water,  there 
is  nothing  further  to  be  desired.  It  is  important,  however,  that  the 
anhydrous  gas  used  in  making  the  solution  of  aqua  ammonia  be  pure; 
and  still  more  important  that  there  be  no  doubt  about  the  purity  of 
such  anhydrous  ammonia  when  it  is  to  be  used  in  compression 
machines.  As  in  the  case  of  carbon  dioxide,  only  a  small  per- 
centage of  non-condensable  or  so-called  permanent  gases  should  be 
tolerated. 

Some  of  the  impurities  found  in  ammonia  damage  the  rubber 
gaskets  and  packing  used  in  the  plant,  and  oil  in  the  system  coats  the 
inside  surfaces  of  the  pipes,  etc.,  so  as  to  interfere  with  efficient  trans- 
fer of  heat.  This  oil  is  removed  by  blowing  out  the  coils  with  steam 
and  air  after  the  ammonia  charge  has  been  removed.  Each  part  of 
the  plant  .may  be  taken  in  its  turn,  the  charge  being  pumped  over 
into  another  part  of  the  system  ad  interim  by  means  of  the  by-passes 
with  which  all  modern  plants  are  provided.  The  purity  of  anhydrous 
ammonia  is  entirely  a  matter  of  keeping  the  system  clean  in  this  way, 
purging  off  the  gases  at  the  condenser,  and  distilling  the  ammonia 
at  periodical  intervals.  At  overhauling  time,  the  charge  of  a  plant 
should  be  withdrawn  and  distilled,  or  sent  to  the  ammonia  factory 
to  be  re-worked  in  case  the  plant  has  no  distilling  facilities.  All  large 
plants  should  be  provided  with  such  apparatus.  In  absorption 
plants,  where  impurities  are  present,  the  ammonia  generator  may  be 


36  REFRIGERATION 

used  to  distill  the  charge  until  practically  all  the  anhydrous  ammonia 
is  removed  from  the  liquor.  This  weak  aqua  ammonia  is  then  dis- 
carded, and  the  solution  made  up  by  adding  clean  water  to  the  system. 
A  practical  engineer  judges  the  purity  of  his  charge  by  the  manner 
in  which  it  acts,  and  has  no  time  to  perform  tests  which  are  entirely 
up  to  the  chemist  and  his  laboratory. 

SYSTEMS  OF  REFRIGERATION 

There  are  two  kinds  of  refrigerating  machines  in  common  use 
— namely,  first,  those  machines  producing  refrigeration  by  means 
of  the  adiabatic  expansion  of  a  non-condensable  gas  performing  work, 
as  the  cold-air  machine;  and  second,  all  those  machines  of  various 
types  which  operate  by  the  vaporization  of  a  volatile  liquid — in 
other  words,  latent-heat  machines.  There  are  three  main  types  of 
these  latter  machines,  known  respectively  as  the  vacuum,  the  absorp- 
tion, and  the  compression  processes  or  systems.  In  some  cases  the 
compression  and  absorption  systems  are  used  in  combination  in  the 
same  plant;  and  in  other  cases  absorption  machines  using  a  dual 
or  combination  liquid  refrigerant  are  employed. 

THE  COLD-AIR  MACHINE 

This  type  of  refrigerating  machine,  of  which  there  are  a  number 
of  constructions  built  principally  in  England  and  continental  Europe, 
was  used  extensively  in  the  early  applications  of  mechanical  refrigera- 
tion on  shipboard;  but  the  machine  is  inherently  of  low  efficiency, 
owing  to  the  fact  that  the  heat  capacity  of  air  is  only  about  0.2377 
B.  T.  U.  per  pound,  or  0.034  B.  T.  U.  per  cubic  foot  for  each  degree 
F.  of  temperature.  On  account  of  this  fact,  the  lower  limit  of  tem- 
perature must  be  made  very  low,  and  this  calls  for  a  comparatively 
large  amount  of  work.  Also,  large  quantities  of  air  must  be 
handled  so  that  the  air  machines  are  of  great  size  for  the  refriger- 
ating duty  produced,  as  compared  with  machines  using  volatile 
liquids.  This  of  course  means  large  frictional  losses,  heavy  wear 
and  tear,  and  increased  maintenance  cost;  so  that,  with  heavy 
first  cost  and  maintenance  cost  standing  against  the  compressed- 
air  machine,  it  is  not  surprising  that  this  type  of  apparatus  has 
been  in  little  favor  since  latent-heat  machines  have  been  per- 
fected. 


REFRIGERATION 


37 


Aside  from  this,  there  is  the  difficulty  with  moisture  in  the  air, 
which  freezes  and  clogs  up  the  system.  As  all  air  contains  a  certain 
amount  of  moisture,  which  is  precipitated  to  a  greater  or  less  extent 
as  the  temperature  is  reduced  in  the  refrigerating  machine,  the  diffi- 
culty with  clogged  passages  is  unavoidable  except  where  special 
apparatus  for  drying  the  air  is  added  to  the  system.  This  of  course 
means  additional  complications  and  increased  cost,  so  that,  all  things 
considered,  the  compressed-air  machine  has  been  in  little  favor  in 
the  United  States,  where  the  design  and  construction  of  latent-heat 
machines  have  been  so  highly  perfected.  Even  in  the  Old  Country, 
where  air  machines  were  formerly  in  high  favor,  they  are  being 
gradually  replaced  by  the  machines  using  volatile  liquids. 


Fig.  2.    General  Ai-rangement  for  Air-Ice  Machine. 

Arrangement  of  Air  System.  Fig.  2  shows  the  general  arrange- 
ment of  the  compressed-air  machine,  the  equipment  consisting  of  a 
single-acting  compression  cylinder  A ;  an  expansion  cylinder  B,  which 
is  also  single-acting;  and  a  condenser  F,  through  which  water  cir- 
culates and  cools  the  compressed  air,  without,  however,  condensing 
it.  At  D  is  shown  a  cold-storage  room  or  refrigerator  kept  cool  by 
the  machine.  In  cylinder  A  the  piston  is  provided  with  suction  valves 
a  and  b,  which  open  inward,  and  a  discharge  valve  c,  opening  out- 
ward, as  shown.  Around  the  cylinder  is  the  water  jacket  J,  which 
removes  part  of  the  heat  generated  by  compressing  the  gas.  The 
diameter  of  cylinder  B  is  a  little  less  than  that  of  cylinder  A,  and  its 
piston  is  solid.  In  the  cylinder-head,  two  valves  are  provided, 
designated  in  the  figure  by  d  and  e,  and  operated  by  the  eccentrics 
C  and  C1,  one  of  these  being  a  suction  and  the  other  a  discharge  valve. 


38  REFRIGERATION 

Connections  are  made  from  the  receiver  E  to  the  condenser  and  to 
the  inlet  valve  d  of  the  expansion  cylinder. 

In  operation,  air  at  atmospheric  pressure  is  taken  into  the  cylin- 
der A  through  the  valves  a  and  b,  and  on  being  compressed  is  dis- 
charged through  the  valve  c  to  the  condenser  F,  where  it  is  cooled. 
At  the  same  time,  the  valve  d  in  the  expansion  cylinder  is  kept  open 
by  the  eccentric  C,  so  that  air  passes  from  the  receiver  E  into  the 
cylinder  until  it  is  filled,  when  the  valve  closes.  The  eccentrics  are 
so  arranged  that  the  valve  d  closes  at  the  beginning  of  the  compression 
stroke  of  the  cylinder  A,  so  that  the  air  in  cylinder  B,  by  its  expansion, 
does  work  and  helps  the  steam  cylinder  (not  shown  in  the  figure)  to 
drive  the  compressor  cylinder.  Cold  air  from  the  expansion  cylinder 
cools  the  refrigerator  D.  In  early  applications  of  the  compressed-air 
machine,  the  cooled  air  coming  from  the  expansion  cylinder  was  dis- 
charged directly  into  the  refrigerator;  but  it  was  found  that  the  mois- 
ture in  the  air,  as  well  as  the  oil  from  the  machine,  by  which  the  air 
was  contaminated,  affected  the  goods  in  storage  so  as  to  make  them 
unpalatable.  Owing  to  this  fact,  the  modern  air  machines  are  ar- 
ranged to  return  the  air  to  the  machine  after  passing  it  through-  the 
cooling  coils  in  the  refrigerators  or  cold  stores  so  that  the  air  is  used 
in  a  continuous  cycle. 

Commercial  Form  of  Air  Machine.  Figs.  3  and  4  give  general 
views  of  the  Allen  dense-air  ice  machine  made  by  H.  B.  Roelker  of 
New  York  City.  There  are  three  main  cylinders  having  slide  valves 
not  unlike  those  used  on  steam  engines,  A  representing  a  steam 
cylinder  arranged  to  drive  the  cylinder  B  in  which  air  at  14.7 
pounds  pressure  is  compressed  to  150  pounds.  The  steam  cylin- 
der is  operated  by  a  single  .D-valve  and  controlled  by  a  throttling 
governor  suitable  for  use  on  shipboard,  where  these  machines 
are  chiefly  employed,  they  being  in  fact  the  standard  for  the 
vessels  of  the  United  States  Navy.  Power  from  the  steam  cyl- 
inder is  transmitted  by  connecting  rod  and  disc  crank,  through 
the  shaft  H,  to  a  center  crank  arranged  to  drive  the  compressor 
cylinder  B.  On  the  opposite  end  of  the  crank-shaft  is  a  third 
crank  disc  to  which  the  connecting  rod  of  the  expansion  cylinder 
is  attached.  In  this  cylinder  the  compressed  air,  after  passing 
through  the  cooling  coil  C,  is  expanded  until  its  temperature 
is  40  to  65  degrees  F.  below  zero.  F  is  a  plunger  piston  pump  for 


REFRIGERATION  39 

circulating  cooling  water  around  the  coils  of  the  tank  C,  and  G  is  a 
priming  air-pump. 

In  the  location  of  the  cylinder  cranks,  the  crank  driving  the  air- 


compressor  leads  the  steam  cylinder  by  about  30  degrees,  this  being 
according  to  the  best  modern  practice.  The  object  of  the  lead  is  to 
apply  the  greatest  pressure  attainable  to  the  piston  of  the  air-corn- 


REFRIGERATION 


41V 


pressor  at  the  time  it  is  completing  its  stroke,  when  the  angle  of  the 
crank-pin  nears  the  position  exerting  the  greatest  effort  on  the  crank 
and  previous  to  the  time  of  cut-off  on  the  steam  cylinders.  By  this 
method  a  much  lighter  fly-wheel  than  otherwise  can  be  used,  since 
the  power  developed  by  the  engine  is  applied  directly  through  the 
shaft,  and  not  transmitted  to  the  fly-wheel  to  be  given  off  when  the 
compressor  cylinder  is  taking  the  maximum  amount  of  power  and  the 
steam  cylinder  is  approaching  the  end  of  its  stroke. 

Compressor  Cylinder.  Suction  is  through  an  opening  in  the 
bottom  of  the  valve  chest,  located  in  the  same  way  as  the  exhaust  on. 
a  slide-valve  engine,  while  discharge  is  through  the  face  of  the  valve 
chest  by  a  passage  similar  to  that  used  for  steam  supply  in  such  an 
engine.  All  valves  are  of  the  slide-valve  type.  The  advantages 
of  this  type  over  the  poppet 
valves  used  on  ammonia  and 
other  compressors  are — com- 
paratively noiseless  action,  no 
hammering  of  seats  or  face  of 
valves  in  closing,  and  absence 
of  unbalanced  pressure  on  the 
valve  to  be  overcome  by  the 
engine. 

An  illustration  of  unbal- 
anced pressure  is  had  in  a 
study  of  Fig.  5.  In  this  dia- 
gram it  is  assumed  that  the 
design  calls  for  a  6-inch  com- 
pressor cylinder  with  a  valve 
seat  of  f-inch  face,  giving  a 
bearing  surface  on  top  of  the 
valve  6f  inches  in  diameter. 
The  area  of  the  cylinder  is 
28.274  square  inches,  while  the  area  of  the  top  of  the  valve,  in- 
cluding the  seat,  is  33.183  square  inches.  With  a  working  pressure 
of  150  pounds,  the  total  pressure  to  open  the  valve  is  150  X  33.183,  or 
4,977.45  pounds.  The  power  exerted  on  the  under  side  of  the'valve 
when  the  pressures  are  equal,  is  28.274  X  150,  or  4,241.1  pounds; 
so  that  in  order  to  open  the  valve,  there  must  be  4,977.45  —  4,241.1 


Fig.  5.    Diagram  Illustrating  Unbalanced 
Valve  Pressure. 


42  REFRIGERATION 

=  636.35  pounds  additional  pressure  applied.  This  means  28.53 
pounds  a  square  inch  in  excess,  or  a  total  pressure  of  178.53  pounds 
a  square  inch  on  the  piston.  This  pressure  is  overcome  by  placing 
springs  or  compressing  chambers  on  top  of  the  valve,  the  latter  being 
preferred.  The  loss  due  to  this  unbalanced  pressure  may  be  as  much 
as  20  per  cent  of  all  the  energy  required  to  compress  the  gas,  besides 
the  wear  and  tear  on  the  valves. 

The  valves  of  the  Allen  machine  are  operated  by  two  rocker 
shafts  which  are  controlled  by  eccentrics  in  the  manner  already 
mentioned.  The  rocker  nearest  the  crankshaft  operates  the  valve 
admitting  steam  to  the  cylinder  A,  and  also  the  rider  valve  on  each 
of  the  air  cylinders.  The  other  rocker  shaft  operates  the  main  valves 
of  the  air  cylinders ;  and  an  arm  extending  horizontally  from  the  cross- 
head  of  the  compressor  cylinder  operates  the  charging  air-pump  and 
the  water-circulating  pump.  The  action  in  the  expansion  cylinder  D 
is  the  same  as  in  a  steam  cylinder  having  slide-valves.  With  an 
initial  pressure  of  260  pounds  and  final  pressure  of  60  pounds,  the 
tempertaure  of  the  cold  air  will  be  from  70  to  90  degrees  below  zero, 
depending  on  the  condition  of  the  machine.  Should  the  pressure  in 
the  expanding  cylinder  become  greater  than  that  in  the  discharge  cham- 
ber due  to  the  distortion  of  rods  or  slipping  of  eccentrics,  the  valves 
will  spring  back  from  their  seats  and  relieve  the  pressure.  Oil  and 
water  traps  and  blow-off  cocks  are  arranged  in  different  parts  of  the 
system  as  shown  in  Fig.  4.  The  cold  air  is  utilized  first  in  an 
ice  box,  filled  with  calcium  brine,  and  then  in  a  refrigerator,  the  air 
passing  finally  through  a  coil  in  a  water-cooler  before  it  returns  to  the 
suction  of  the  compressor  cylinder. 

Operation  of  the  Allen  machine,  according  to  the  rules  used  in 
the  United  States  Navy,  should  be  as  follows : 

On  starting  the  machine,  have  the  blow-valves  of  the  expansion  cylinder 
and  the  pet-cocks  of  the  various  traps  open  until  no  more  grease  or  water  dis- 
charges. The  two  IJ-or  2-inch  valves  of  the  main  pipes  must  be  open,  and  the 
1-inch  by-pass  pipe  closed;  also  the  ^-inch  hot-air  valves  from  the  compressor 
to  the  expander  cylinder  must  be  closed. 

Be  sure  that  the  circulating  water  is  in  motion.  The  full  pressure  is  60 
to  65  Ibs.  low  pressure,  and  210  to  225  Ibs.  high  pressure. 

During  the  running,  open  the  pet-cocks  of  the  water-trap  in  order  to  take 
the  water  out  of  the  air  from  the  primer  pump  frequently  enough  so  that  it  will 
never  be  more  than  half-filled.  If  the  water  should  be  allowed  to  enter  the 
main  pipes,  it  is  liable  to  freeze  and  clog  at  the  valves.  By  keeping  all 


REFRIGERATION  43 

stuffing-boxes  well  lubricated  by  the  lubricator  cups,  the  pressures  are  easily 
maintained  with  but  little  screwing-up  of  the  packing.  If  the  low-air  pressure 
is  not  maintained,  the  fault  is  almost  always  due  to  leaks  at  the  stuffing-boxes. 
Under  all  circumstances  it  is  due  to  some  leak  into  the  atmosphere,  as  the  primer 
pump  valves  have  never  yet  been  found  to  be  at  fault. 

The  packing  of  valve-stems  and  piston-rods  consists  of  a  few  inner  rings 
of  Katzenstein's  soft  metal  packing,  then  a  hollow  greasing  ring,  then  soft 
fibrous  packing  (Garlock  packing). 

The  sight-feed  lubricators  of  the  compressor  and  expander  should  use 
only  a  light,  pure,  mineral  machine  oil  from  which  the  paraffine  has  been  re- 
moved by  freezing — usually  three  drops  per  minute  in  the  compressor,  and  one 
or  two  in  the  expander. 

The  pistons  of  the  compressor  and  expander  cylinders  are  packed  with 
cup  leathers,  which  commonly  last  about  one  or  two  months  of  steady  work. 
When  these  leathers  give  out,  the  high  pressure  decreases  in  relation  to  the  low 
pressure,  and  the  apparatus  shows  a  loss  of  cold.  A  leak  at  any  other  point 
of  high  pressure  into  low  pressure  will  have  the  same  effect.  These  packing 
leathers  are  made  of  thick  kip  leather,  or  of  white  oak-tanned  leather  of  some- 
what less  than  J-inch  thickness.  They  are  cut  |-inch  larger  in  diameter  than 
the  cylinders.  The  leathers  must  be  kept  soaked  with  castor  oil  and  must  be 
well  soaked  in  that  before  using;  and  a  tin  box  containing  spare  leathers  and 
castor  oil  must  be  kept  on  hand. 

Once,  or  sometimes  twice  a  day,  it  is  necessary  to  clean  the  machine  by 
heating  it  up  and  blowing  out  all  the  oil  and  ice  deposits.  This  is  done  as  follows: 
The  1-inch  valve  of  the  by-pass  is  opened.  Then  the  two  1J-  or  2-inch  valves 
in  the  main  pipes  are  closed;  then  the  two  %-inch  valves  in  the  hot-air  pipe 
from  the  compressor  chest  to  the  expander  are  opened,  and  the  IJ-inch  valve 
of  the  expander  inlet  is  partially  closed;  then  the  live  steam  is  let  slowly  into  the 
jacket  of  the  oil-trap,  keeping  the  outlet  from  the  steam  jacket  open  enough 
to  drain  the  condensed  steam. 

Run  in  this  manner  for  about  one-half  hour;  during  this  time,  frequently 
blow  out  the  bottom  valve  of  the  oil  trap,  also  the  blow-off  from  the  expander, 
until  everything  appears  clean.  Then  shut  off  the  steam,  and  drain  connections 
of  the  jacket  of  the  trap  and  the  hot-air  pipe  from  the  compressor  to  the  ex- 
pander. Then  open  the  two  IJ-inch  valves  in  main  pipes.  Then  close  the 
1-inch  by-pass  pipe  and  all  pet-cocks,  and  run  as  usual. 

Whenever  opportunity  offers  to  blow  out  the  manifolds  of  the  meat-room 
and  the  ice-making  box  (that  is,  whenever  they  are  thawed),  this  should  be 
done.  If  it  is  suspected  that  a  considerable  quantity  of  oil  and  water  has  got 
into  the  pipe  system  and  is  clogging  the  areas  and  coating  the  surfaces,  the 
pipes  can  be  cleaned  by  running  hot  air  through  them  as  is  done  during  the 
daily  cleaning  of  the  machine.  The  oil  and  water  are  then  drawn  off  at  the 
bottom  of  the  ice-making  box  and  the  manifolds  of  the  refrigerating  coils. 

The  clearance  of  the  two  air  pistons  and  of  the  primer  plunger  is  only 
^-inch;  therefore  not  much  change  of  piston-rods  and  connecting  rods  is  per- 
missible, and  when  the  piston  nuts  are  unscrewed  to  change  the  piston  leathers, 
the  rod  should  be  watched  that  it  does  not  unscrew  from  the  cross-head.  When- 
ever it  is  noticed  that  the  brine  freezes,  more  chloride  of  calcium  should  be 
added,  and  should  be  well  stirred  into  the  brine. 


44  REFRIGERATION 

VACUUM  PROCESS 

In  machines  working  on  the  vacuum  system,  the  essential  feature, 
as  the  name  implies,  is  production  of  a  vacuum  in  the  vessel  contain- 
ing the  liquid  to  be  cooled.  Probably  the  first  machine  constructed 
on  this  principle  was  that  invented  by  Dr.  Cullen  in  1755.  His 
apparatus  has  served  as  a  pattern  for  all  later  types.  In  some  as- 
pects, the  vacuum  machine,  as  to  its  principle  of  operation,  resembles 
the  latent-heat  machines  using  volatile  liquids,  in  all  of  which  evapora- 
tion is  had  under  comparatively  low  pressures,  the  difference  being 
that,  in  the  case  of  the  vacuum  process,  the  pressure  is  very  much 
lower  than  with  the  other  latent-heat  machines.  Thus,  with  an 
ammonia  compression  machine,  the  back-pressure  in  the  suction 
coils  may  be  from  15  to  25  pounds,  or  possibly  more  in  some  cases; 
whereas,  with  the  vacuum  process,  it  is  necessary  to  have  the  vacuum 
as  good  as  possible  with  the  best  pumps  made,  there  being  only 
about  0.1  pound  pressure  per  square  inch,  this  being  necessary 
where  water  is  to  be  frozen  by  evaporation  of  water,  as  its  tem- 
perature of  evaporation  is  too  high  to  get  good  freezing  for  pres- 
sures any  higher  than  this. 

In  ordinary  practice,  the  discharge  of  the  vacuum  pump  is  con- 
nected to  a  condenser  in  which  the  pressure  is  about  1.5  pounds. 
About  one-fifth  the  water  put  into  the  vacuum  chamber  is  evaporated, 
so  that  for  each  five  tons  of  water  used  there  is  a  net  return  of  about 
four  tons  of  ice.  Under  the  best  conditions  less  water  will  be  evapo- 
rated with  a  better  return.  About  340  gallons  of  condensing  water 
is  required  per  ton  of  refrigeration,  assuming  a  temperature  range  of 
30  degrees.  The  vapor  cylinder  must  be  about  150  times  as  large 
as  the  cylinder  of  an  ammonia  latent-heat  machine  of  equal  capacity. 
This  enormous  size  of  cylinder  places  the  vacuum  machine  out  of 
competition  with  other  apparatus  on  the  market;  and  to  get  around 
this  difficulty  inventors  have  developed  various  modifications  of  the 
machine,  using  various  substances  to  absorb  the  vapor  chemically, 
the  most  practical  apparatus  of  this  kind  being  that  employing  sul- 
phuric acid  as  an  absorbent. 

Fig.  6  is  a  diagram  showing  the  arrangement  of  parts  in  the  sul- 
phuric acid  vacuum  machine,  the  air-pump  P  being  employed  to 
produce  a  vacuum  in  the  chamber  A,  so  that  the  water  in  this  cham- 
ber begins  to  evaporate.  Vessel  B  contains  sulphuric  acid,  which 


REFRIGERATION 


45 


is  allowed  to  fall  into  vessel  C  in  the  form  of  spray.  Since  the  acid 
has  a  great  affinity  for  water,  it  will  absorb  the  vapor  in  the  chamber 
A,  and,  after  being  thus  diluted,  will  flow  to  the  vessel  D.  An  in- 
jector F  is  arranged  to  supply  fresh  water  to  the  vessel  A,  and  at  the 
same  time  to  draw  the  brine  from  the  coils  E,  brine  being  used  in  A 
as  it  is  not  de- 
sired to  do  the 
freezing  direct 
in  this  vessel. 
Brine  from  the 
vessel  A  is  cir-  - 
culated  through 
the  coil  E  in  the 
refrigerator,  in 
a  closed  cycle. 
A  pump  (not 
shown  in  the  il- 


Fig.  6.    Diagram  of  Sulphuric  Acid  Vacuum  Machine. 


lustration)  is  used  to  return  the  acid  from  the  reconcentrator  to 
vessel  B  to  be  used  over  again.  The  chief  objection  to  this  type 
of  machine  is  the  fact  that  the  pipes  must  be  made  of  lead  or  lined 
with  lead  in  order  to  prevent  corrosion. 

Aside  from  the  size  of  the  apparatus  and  the  difficulty  in  using 
the  acid,  the  vacuum  system  involves  considerable  complication  in 
the  pumping  apparatus,  as  it  is  difficult  to  keep  the  packing  glands 
and  joints  of  the  vacuum  pumps  tight  for  the  low  pressure  required. 
Ice  produced  by  this  system  is  not  of  good  quality,  it  being  porous  or 
opaque  unless  frozen  in  specially  prepared  moulds  previously  chilled, 
which  process  is  too  expensive  for  commercial  use.  Owing  to  the 
necessity  for  circulating  the  acid  and  cooling  water,  about  10  or  12 
tons  of  liquid  must  be  handled  for  each  ton  of  ice  produced ;  and  in 
doing  this  about  180  pounds  of  coal  are  burned,  this  being  the  fuel 
necessary  to  supply  steam  to  the  pumps  and  heat  the  coils  of  the  acid 
evaporator  used  in  reconcentrating. 

Vacuum  Pump.  Many  pumps  have  been  developed  for  use  in 
the  vacuum  process  of  refrigeration ;  but  one  typical  of  others  is  that 
of  Lange,  which  is  illustrated  in  Fig.  7.  In  this  pump  three  pistons 
are  employed,  as  indicated  in  the  illustration  by  the  letters  A,  B, 
and  C,  the  arrangement  being  such  that  the  pistons  are  in  vertical 


REFRIGERATION 


line  one  above  the  other,  with  each  working  in  its  own  cylinder.     The 
three  cylinders  are  connected  by  valves  as  shown,  the  valves  being 

sealed  with  oil  and  so  ar- 
ranged that  each  of  the  pis- 
tons exhausts  the  contents 
of  the  cylinder  below  it.  On 
leaving  the  top  cylinder,  the 
mixed  oil  and  air  is  dis- 
charged into  the  separator 
D,  from  which  the  air  is 
allowed  to  escape  into  the 
atmosphere,  while  the  oil 
passes  to  the  receptacle  be- 
low. From  this  receptacle 
the  oil  is  returned  to  the 
chamber  in  the  lower  end 
of  the  pump  as  needed. 

About  the  only  vacuum 
plant  of  any  importance  in 
Fig.r.  Lange's  vacuum  Air  Pump,  the  United   States   is    the 

100-ton   establishment  of  the  Patten   Vacuum    Ice    Machine  Co., 
Baltimore,  Md.  This  plant  has  been  in  operation  for  some  years. 

ABSORPTION  SYSTEM 

This  depends  for  its  operation  on  the  affinity  of  certain  liquids 
for  each  other  and  on  the  process  of  fractional  distillation — that  is, 
the  distilling  of  one  or  more  liquids  from  a  solution  under  such  con- 
ditions of  temperature  and  pressure  that  the  other  liquids  do  not 
vaporize  and  are  left  behind.  When  a  liquid  can  be  vaporized  readily 
and  the  resulting  vapor  is  easily  absorbed  by  another  liquid,  we  have 
the  complete  set  of  conditions  for  the  absorption  system.  In  some 
respects  this  system  is  like  the  vacuum  process,  while  in  other  respects 
it  is  similar  to  the  compression  system.  The  difference  from  the  one 
is  the  absorption  of  the  gas  by  water  instead  of  by  acid;  from  the 
other,  the  compression  of  gas  by  direct  application  of  heat  in  the  gen- 
erator instead  of  by  mechanical  action,  as  in  the  compressor.  Mention 
has  already  been  made  of  the  great  affinity  of  ammonia  for  water,  on 
account  of  which  practically  all  absorption  machines  use  aqua 
ammonia  for  the  working  medium. 


REFRIGERATION 


47 


Carry's  Experimental  Absorption 
Machine. 


For  the  invention  of  the  absorption  process,  the  world  is  indebted 
to  Ferdinand  Carre,  brother  of  Edmund  Carre,  inventor  of  the  sul- 
phuric acid  machine,  who  made  a  study  of  the  phenomena  of  evapora- 
tion and,  about  the  year  1850,  evolved  the  primitive  absorption  ap- 
paratus, shown  in  Fig.  8,  consisting  of  two  strong  iron  jars  connected 
together  by  an  iron  pipe.  Jar  A  was  used  as  the  ammonia  still  or 
generator  and  had  placed  in  it  a  quantity  of  strong  ammonia  solution. 
A  spirit  lamp  placed  under 
the  jar  supplied  the  heat 
necessary  for  distillation, 
and  an  air  cock  I  afforded 
the  means  of  venting  off  the 
air  as  soon  as  the  jar  became 
heated.  With  continued  ap- 
plication of  heat,  the  pres- 
sure increased  in  all  parts 
of  the  system.  Jar  C  was 
placed  in  a  tank  and  sur-  Fig. 

rounded  by  cold  water  D,the 
supply  being  changed  constantly  so  as  to  maintain  the  original  tem- 
perature at  about  60°  F.  Ammonia  vaporized  in  the  jar  A  passed 
to  the  jar  C  and  was  liquefied  by  the  cooling  of  this  jar  at  about  120 
pounds  pressure.  At  this  pressure  the  boiling  temperature  of  water 
is  230°  F.,  so  that  vaporization  of  water  was  impossible  under  the 
conditions  prevailing. 

When  the  process  of  distilling  ammonia  was  completed,  the  lamp 
was  removed  from  jar  A,  the  water  drawn  off  from  around  jar  C,  and 
the  tank  D  filled  with  whatever  substance  it  was  desired  to  freeze. 
A  water  pipe  allowed  water  to  flow  over  jar  A  and  cool  its  contents, 
with  the  result,  that  the  pressure  was  removed  from  both  the 
jars,  and  the  liquid  anhydrous  ammonia  in  jar  C  began  to  vaporize 
and  return  to  jar  A,  where  it  was  absorbed  by  the  water  from  which 
it  had  been  distilled.  By  the  change  of  anhydrous  ammonia 
from  the  liquid  into  the  gaseous  form,  the  heat  was  taken  from 
the  liquid  in  the  tank  D,  and  held  latent  by  the  gas,  so  that  this 
liquid  was  cooled.  This  same  heat  was  given  up  as  the  gas  was 
reabsorbed  in  the  jar  A,  and  was  transferred  to  the  cooling  water 
passing  over  the  jar. 


48  REFRIGERATION 

The  intermittent  action  of  Carry's  machine  makes  it  imprac- 
ticable for  anything  more  than  experimental  uses;  and  for  the  decade 
following  its  invention,  great  efforts  were  made  by  inventors  to  im- 
prove the  apparatus  in  such  a  way  as  to  get  continuous  operation. 
This  was  finally  accomplished  about  1858.  The  apparatus  then 
developed,  similar  in  a  general  way  to  that  employed  at  the  present 
time,  consisted  of  three  distinct  sets  of  appliances:  the  first,  for  dis- 
tilling and  liquefying  the  ammonia;  the  second,  for  producing  cold 
by  means  of  an  evaporator  and  an  absorber;  and  the  third,  for  pump- 
ing the  rich  liquor  from  the  absorber  to  the  generator,  from  which  the 
cycle  is  started  afresh.  These  three  operations  are  distinct,  but  the 
apparatus  in  each  part  of  the  plant  is  dependent  on  all  the  other  parts, 
so  that  all  must  operate  continuously  when  in  use  in  order  to  form  a 
complete  closed  cycle.  Fig.  9,  taken  from  the  Southern  Engineer, 
is  a  good  diagram  illustration  of  an  absorption  plant,  consisting  of  an 
ammonia  boiler  or  generator  /,  an  analyzer  E,  exchanger  B,  con- 
densing coils  F,  cooler  C,  absorber  D,  receiver  G,  and  the  ammonia 
pump/. 

The  Generator.  The  generator  is  a  cylindrical  drum  containing 
coils  of  pipe  through  which  steam  from  the  boiler  is  circulated  for 
distilling  the  ammonia.  This  part  of  the  apparatus,  which  is  also 
known  as  the  ammonia  still,  is  constructed  in  several  forms,  both 
horizontal  and  vertical.  The  horizontal  generator  is  the  more  ex- 
pensive of  the  two  forms,  but  has  the  advantage  of  supplying  drier 
gas.  In  the  vertical  generator,  the  evaporating  surface  is  compara- 
tively small  and  the  boiling  so  rapid,  that  it  is  difficult  to  keep  the 
steam  coils  covered  with  liquor.  These  coils,  when  uncovered,  be- 
come pitted  by  the  combined  action  of  the  gas  and  the  ammonia 
liquor.  Generators  of  the  vertical  type  are  also  likely  to  boil  over, 
when  forced,  and  the  height  is  inconveniently  great  when  properly 
installed  in  connection  with  the  analyzer. 

Analyzer.  This  apparatus  is  set  directly  above  the  generator 
and  connects  thereto,  as  shown  at  E  in  the  illustration.  It  consists 
ordinarily  of  a  cylindrical  drum  containing  a  series  of  pans  or  de- 
flectors over  which  the  hot  distilled  gas  must  pass  for  the  purpose  of 
separating  any  water  that  may  have  been  distilled  or  carried  over 
with  the  ammonia  gas.  The  water  thus  separated  is  drained  back 
into  the  generator.  Rich  ammonia  liquor,  being  returned  from  the 


REFRIGERATION 


49 


50  REFRIGERATION 

absorber  to  the  generator,  is  discharged  from  the  ammonia  pump  into 
the  top  of  the  analyzer.  It  flows  over  the  pans  in  such  a  way  as  to 
absorb  heat  from  the  gas.  This  results  in  a  saving  of  steam  required 
to  heat  the  generator,  as  well  as  in  the  amount  of  water  required  at 
the  condenser  to  liquefy  the  ammonia  gas. 

The  Condenser.  The  condenser  F  is  a  series  of  pipes  over  which 
water  flows,  cooling  the  dry  gas,  which  liquefies  under  the  pressure 
created  in  the  generator.  The  liquid  ammonia  flows  to  the  receiver 
G.  It  is  then  ready  to  be  passed  to  the  cooling  coils  through  the  ex- 
pansion valves,  which  are  adjusted  to  supply  the  amount  of  liquid 
required  to  accomplish  the  desired  cooling. 

Rectifier.  This  is  an  apparatus  added  to  the  absorption  plant 
in  recent  years  with  a  view  to  giving  increased  efficiency.  It  is  not 
shown  in  the  illustration  but  is  usually  mounted  on  top  of  the  genera- 
tor in  connection  with  the  analyzer.  The  construction  varies  with 
different  makes  of  machines,  the  object  in  all  cases  being,  to  remove 
moisture  from  the  gas  coming  to  the  analyzer,  as  moisture  is  very 
detrimental  to  the  operation  of  the  absorption  machine.  The  most 
usual  construction  consists  of  a  nest  of  tubes  enclosed  in  a  cylinder 
having,  at  the  bottom,  a  chamber  for  collecting  the  moisture  separated 
from  the  gas.  The  rich  liquor  from  the  absorber  is  taken  through 
these  tubes,  either  before  or  after  passing  through  the  heat  exchanger, 
and  goes  thence  to  the  top  of  the  analyzer.  The  gas,  on  its  way 
to  the  condenser,  passes  through  this  cylinder,  surrounds  the  tubes 
and  is  thus  cooled  sfficiently  to  cause  any  moisture  that  it  may  con- 
tain to  be  precipitated.  In  some  cases  the  rectifier  is  in  the  form  of 
a  pipe  coil  similar  to  the  ordinary  atmospheric  or  double-pipe  conden- 
ser, in  which  case  care  must  be  taken  to  avoid  supplying  cooling  water 
sufficient  to  cause  condensation  of  the  ammonia  in  the  apparatus. 

The  Equalizer.  The  equalizer  or  heat  exchanger  B,  as  shown 
in  the  illustration,  is  a  drum  in  which  are  several  coils  of  pipe  through 
which  the  liquor  from  the  pump  I  is  forced  on  its  way  to  the  generator 
J.  The  pipes  in  the  drum  are  surrounded  by  the  hot  weak  liquor 
entering  at  the  top  through  the  pipe  U  from  the  generator.  Thus 
the  hot  liquor  is  made  to  give  up  heat  to  the  rich  liquor  in  the  coils, 
on  its  return  passage  to  the  generator.  In  horizontal  machines 
properly  proportioned,  at  least  6  square  feet  of  exchange  surface  should 
be  allowed  for  each  ton  of  refrigerating  capacity.  This  cannot  be 


REFRIGERATION  51 

done  with  machines  using  vertical  generators,  owing  to  the  increased 
danger  of  boiling  over.  In  such  machines  it  is  not  practicable  to 
allow  much  more  than  2  square  feet  of  exchange  surface  per  ton. 
This,  however,  Is  not  sufficient  to  reduce  the  temperature  of  the  weak 
liquor  much  below  135°  F.,  so  a  special  weak  liquor  cooler  C  is  em- 
ployed. 

Even  with  the  horizontal  generator,  this  cooler  is  sometimes 
employed  to  advantage,  as  shown  in  Fig.  9.  The  cooler  in  this,  as  in 
most  instances,  is  of  drum  shape  similar  to  the  exchanger,  and  con- 
tains a  coil  of  pipe  through  which  water  is  circulated  for  cooling  the 
liquor  coming  from  the  exchanger  on  its  way  to  the  absorber.  The 
liquor  flows  from  the  cooler  to  the  absorber  through  the  pipe  V,  a 
regulating  valve  being  placed  on  this  pipe  at  the  absorber,  in  the  best 
practice.  Where  the  equalizer  and  rectifier  are  both  used,  the  rich 
liquor  passing  through  them  returns  to  the  generator  at  a  compara- 
tively high  temperature.  It  must  not  be  forgotten  that — the  higher 
the  temperature,  the  less  the  moisture  removed  by  the  liquor  in  the 
analyzer.  On  this  account  rectifiers  are  frequently  made  to  use  cool- 
ing water,  and  as  the  water  so  used  can  be  passed  over  the  ammonia 
condensers  after  leaving  the  rectifier,  there  is  not  much  added  expense 
on  account  of  water.  Rectifiers  of  this  type  are  made  in  pipe  coils, 
as  above  mentioned. 

Absorber.  This  part  of  the  apparatus  D,  performs  the  reverse 
operation  to  that  performed  in  the  generator.  Heat  supplied  in  the 
generator  separates  the  ammonia  from  the  solution,  while  in  the 
absorber  the  weak  aqua  ammonia  absorbs  the  gas  at  low  temperature 
produced  by  cooling  water.  The  absorber  shown  in  the  illustration 
is  similar  in  general  form  to  the  weak  liquor  cooler,  which  consists 
of  a  number  of  cooling  coils  in  a  cylindrical  shell,  water  being  cir- 
culated through  the  coils  to  give  the  desired  reduction  of  temperature. 
The  construction  shown  is  known  as  the  empty  form  of  absorber, 
which  is  about  the  most  satisfactory  design  yet  evolved.  The  weak 
liquor  is  sprayed  into  the  shell  of  the  absorber  at  the  top,  pass- 
ing down  over  the  cooling  coils  and  coming  in  contact  with  the 
gas,  which  is  admitted  in  the  form  of  spray  near  the  bottom  of 
the  chamber.  Thus  absorption  of  gas  is  rapid  and  continuous, 
the  rich  liquor  being  drawn  off  from  the  bottom  of  the  absorber 
as  shown. 


52  REFRIGERATION 

In  another  form  of  apparatus  known  as  the  submerged  or  tank 
absorber,  a  series  of  coils  is  so  arranged  in  the  containing  shell  that 
the  gas  enters  them  at  the  top,  together  with  a  spray  of  the  weak 
liquor,  which  absorbs  the  gas  in  descending  through  the  coils.  A 
receiver  at  the  bottom  of  the  tank  stores  the  rich  liquor,  and  cooling 
water  entering  the  shell  near  the  bottom  fills  the  space  surrounding 
the  coils  and  flows  off  at  the  top,  the  drum  leing  full  of  water.  With 
this  type  of  apparatus  about  35  square  feet  of  surface  should  be 
allowed  per  ton  of  capacity.  In  the  fvtt  absorber,  coils  are  nested  in 
a  cylindrical  shell  into  which  the  gas  and  weak  liquor  are  admitted 
at  the  bottom,  so  that  the  gas  is  compelled  to  pass  through  the  entire 
body  of  ammonia  liquor  in  the  shell.  This  gives  complete  absorp- 
tion, but  there  is  the  disadvantage  incident  to  a  loss  of  pressure 
equal  to  the  head  of  liquid  between  the  top  level  of  the  liquor  and 
the  gas  inlet. 

Ammonia  Pump.  As  it  is  desirable  to  have  means  for  testing 
the  piping  of  a  plant  to  350  or  400  pounds  pressure,  the  ammonia 
pump  shouU  be  selected  with  this  in  view,  notwithstanding  the  fact 
that  in  its  ordinary  work  there  is  only  the  pressure  of  the  generator 
to  work  against.  Care  should  be  taken  in  selecting  the  materials 
and  constructing  the  pump  in  order  to  make  it  proof,  as  far  as  pos- 
sible, against  the  action  of  ammonia.  The  stuffing-box  gland  should 
be  particularly  designed  to  prevent  leakage.  It  should  have  good 
depth  so  that,  with  good  ammonia  packing,  the  gland  need  not  be 
set  up  tight  enough  to  prevent  leakage,  thereby  causing  loss  of  work 
in  friction  and  perhaps  damaging  the  piston  rod  so  that  it  will  have 
to  be  renewed  or  turned  down.  As  duplex  pumps  have  more  mov- 
ing parts  and  more  glands  requiring  attention  than  single-acting 
pumps,  such  pumps  are  not  suitable  for  use  in  pumping  aqua  am- 
monia, so  that  single-acting  pumps  are  invariably  used  in  both  the 
vertical  and  horizontal  types,  arranged  for  direct  steam  drive  or  drive 
by  power.  As  the  ammonia  pump  is  vital  to  the  operation  of  the 
plant  it  should  be  of  the  very  best  construction,  and  in  large  plants 
duplicate  pumps  should  be  installed.  Some  manufacturers  provide 
this  duplicating  feature  also  for  the  small  plants,  by  specially  con- 
structing the  pumps  with  duplicate  cylinders,  that  can  be  driven  by 
power  or  steam,  only  one  of  the  cylinders  being  required  in  ordinary 
operation. 


REFRIGERATION  53 

Ammonia  Regulator.  As  in  the  absorption  system,  regulation 
of  the  working  depends  principally  on  the  strength  of  the  rich  liquor 
supplied  to  the  still,  it  is  desirable  that  the  density  of  this  liquor  be 
as  constant  as  possible  at  the  given  figure  for  which  the  machine  is 
designed  to  operate,  this  ordinarily  being  about  26  degrees  on  the 
Baume  scale.  With  the  full  absorbers  and  other  types  where  quan- 
tities of  the  weak  liquor  come  in  contact  with  the  gas  to  be  absorbed, 
the  regulation  of  density  in  the  rich  liquor  is  simple;  but  with  the 
empty  absorber,  which  is  preferable  on  other  accounts,  it  is  necessary 
to  regulate  the  supply  of  weak  liquor  carefully,  if  the  density  is  to  be 
maintained  constant.  For  this  purpose  ammonia  regulators  are 
used  on  the  absorber,  governing  the  flow  of  weak  liquor,  the  density 
of  which  is  16°  to  18°  Bourne*. 

Operation.  As  steam  is  turned  into  the  generator,  the  rich 
liquor  is  heated  and  ammonia  gas  distilled.  This  gas  rises  into  the 
analyzer  E,  and,  coming  in  contact  with  the  pans  or  deflecting  sur- 
faces and  the  rich  liquor  at  lower  temperature,  is  cooled  so  that  what 
steam  it  contains  is  condensed,  leaving  the  gas  free  of  moisture  as  it 
leaves  the  analyzer  for  the  condenser,  or  for  the  rectifier  when  this 
apparatus  is  used  to  ensure  absolute  dryness.  The  hot  dry  gas  enters 
the  condensing  coils  at  the  top  as  shown,  flowing  downward ;  and  the 
cooling  water  flows  over  the  coils  F  from  the  pipe  W,  so  as  to  cool 
the  gas  until  it  condenses  under  the  pressure  of  the  system.  The 
liquid  anhydrous  ammonia  thus  formed  flows  into  the  receiver  G  and 
thence  to  the  expansion  valve  H  from  which  it  passes  to  the  cooling 
coils  M.  The  condensing  pressure  is  from  150  to  200  pounds.  Modi- 
fications may  be  found  in  some  plants  causing  them  to  vary  from  the 
plan  shown,  but  an  understanding  of  the  plant  illustrated  in  Fig.  9 
will  enable  the  student  to  handle  any  equipment,  the  prinicples  being 
the  same  as  here  set  forth. 

Power  for  Absorption  Plant.  In  computing  the  size  of  boiler 
required  for  an  absorption  machine,  it  is  first  necessary  to  find  the 
heat  required  in  the  generator  which  the  boiler  is  to  supply.  The 
weight  of  steam  corresponding  to  this  amount  of  heat  added  to  the 
weight  of  steam  required  for  the  operation  of  the  auxiliary  machines 
gives  the  total  weight  of  steam  necessary,  and  from  this  data  the  size 
boiler  which  will  deliver  the  required  amount  of  steam  continuously 
is  computed. 


54 


REFRIGERATION 


The  heat  required  in  the  generator  is  equal  to  the  heat  lost  in 
the  condensing  coils  added  to  the  heat  lost  in  the  absorber,  minus 
the  heat  gained  in  the  cooling  coils,  minus  the  heat  gained  by  the 
work  of  the  ammonia  pump  in  raising  the  rich  liquor  from  the  pres- 
sure in  the  absorber  to  the  pressure  in  the  generator. 

The  heat  lost  in  the  condensing  coils  is  equal  to  the  temperature 
of  the  entering  gas,  minus  the  temperature  of  the  liquid  ammonia,  plus 
the  latent  heat  of  ammonia.  Latent  heat  of  ammonia  is  found  by 
the  rule,  555.5-(0.613  X  temp.) -(0.0002 19  X  sq.  of  temp). 

TABLE  XV 
Heat  Generated  by  Absorbing  Ammonia 


AMMONIA  IN 
POOR  LIQUOR, 
PER  CENT 

AMMONIA  IN 
RICH  LIQUOR, 
PER  CENT 

HEAT  OF  ABSORP- 
TION BY  ONE 
POUND  OF  AM- 
MONIA IN  UNITS 

POUNDS  OF  RICH 
LIQUOR  FOR  EACH 
POUND  OF  ACTIVE 
AMMONIA 

a 

c 

Ha 

Pr 

10 

25. 

812 

6.0 

10 

36 

828 

3.45 

12 

35.5 

828 

3.74 

14 

25 

854 

7.8 

15 

35 

811 

4.25 

17 

28.75 

840 

7.0 

20 

25 

840 

16.0 

20 

33 

819 

6.1 

20 

40 

795 

4.0 

The  heat  lost  in  the  absorber  is  equal  to  the  heat  produced  by 
the  absorption  of  one  pound  of  ammonia  by  the  poor  liquor,  plus 
the  heat  brought  into  the  absorber  by  a  corresponding  amount 
of  poor  liquor  (per  cent  ammonia  in  rich  liquor  -5-  per  cent  of 
ammonia  in  poor  liquor)  and  the  negative  heat  produced  by  one 
pound  of  gas  from  the  cooling  coils.  Table  XV  gives  the  heat 
generated  in  the  absorber  per  pound  of  gas  under  various  con- 
ditions. 

The  heat  brought  into  the  absorber  by  the  poor  liquor  for  each 
pound  of  active  ammonia  gas  is  equal  to  the  number  of  pounds  of  rich 
liquor  for  each  pound  of  active  ammonia  minus  the- difference  in  tem- 
perature between  the  incoming  poor  liquor  and  the  outgoing  rich 
liquor.  The  specific  heat  of  the  poor  liquor  may  be  taken  as  1, 
and  disregarded. 


REFRIGERATION  55 

The  negative  heat  brought  into  the  absorber  is  equal  to  the 
difference  in  temperature  between  the  outgoing  rich  liquor  and  the 
gas  in  the  cooling  coils,  multiplied  by  the  constant  0.5. 

The  heat  absorbed  by  one  pound  of  the  refrigerant  in  the  cool- 
ing coils  while  doing  work  is  equal  to  the  latent  heat  of  ammonia, 
plus  the  difference  in  the  temperatures  of  the  ammonia  liquid  and 
the  refrigerator,  multiplied  by  the  specific  heat  of  ammonia. 

The  heat  produced  by  the  pump  is  that  generated  by  raising  the 
rich  liquor  from  the  pressure  in  the  absorber  to  that  in  the  generator, 
and  in  approximate  calculations  may  be  disregarded.  It  may  be 
found  by  the  following  rule : 

Heat  produced  is  equal  to  the  weight  of  rich  liquor  to  be  pumped  multi- 
plied by  the  difference  between  the  height  in  feet  of  a  column  of  water  one  square 
inch  in  area  which  will  give  the  pressure  in  the  generator,  and  the  height  of  a 
similar  column  of  water  giving  the  pressure  in  the  absorber.  This  amount  is  to 
be  divided  by  the  specific  gravity  of  the  rich  liquor  multiplied  by  the  con- 
stant 778. 

The  weight  in  pounds  of  rich  liquor  to  be  circulated  for  each 
pound  of  liquid  ammonia  obtained  in  G  is  equal  to  100  minus 
the  percentage  of  ammonia  in  the  poor  liquor,  divided  by  the  dif- 
ference between  the  percentage  of  ammonia  in  the  poor  liquor 
and  the  percentage  of  ammonia  in  the  rich  liquor.  A  column 
of  water  one  square  inch  in  area  and  2.3  feet  high  weighs  one 
pound. 

After  finding  the  heat  required  per  hour  by  the  generator  for 
each  pound  of  rich  liquor  entering,  the  total  heat  required  per  hour 
will  be  equal  to  the  heat  in  one  pound  multiplied  by  the  number  of 
pounds  of  rich  liquor  circulated  in  an  hour.  The  weight  of  rich 
liquor  circulated  in  an  hour  may  be  found  by  multiplying  the  area  of 
the  pump  cylinder  in  square  inches  by  the  length  of  stroke  in  inches, 
and  by  the  number  of  strokes  an  hour,  and  dividing  this  amount  by 
27.7.  This  result  should  be  multiplied  by  the  specific  gravity  of  the 
rich  liquor. 

We  now  have  the  number  of  British  thermal  units  required  per 
hour  in  the  generator.  This  number  divided  by  the  latent  heat  of 
steam  corresponding  to  the  generator  pressure  gives  the  pounds  of 
steam  required. 

The  weight  of  steam  required  for  the  auxiliaries  may  be  calcu- 
lated as  follows 


56  REFRIGERATION 

Weight  of  steam  per  hour  for  each  steam  cylinder  equals  0.0348  X  the 
square  of  the  diameter  of  the  cylinder  X  the  length  of  stroke,  both  in  inches, 
X  the  number  of  strokes  per  minute  X  the  density  or  weight  of  one  cubic  foot 
of  the  steam  at  the  initial  pressure. 

The  sum  of  the  weight  of  steam  required  by  the  generator  and 
that  required  by  all  the  auxiliaries  gives  the  total  amount  of  steam 
required  per  hour  to  distill  the  ammonia  from  the  rich  liquor  and  to 
operate  all  the  machinery  about  the  plant.  The  total  weight  of 
steam  divided  by  13.8  gives  the  number  of  square  feet  of  effective 
heating  surface  required  in  the  boiler. 

Binary  Systems.  In  the  development  of  the  absorption  machine, 
many  experiments  have  been  made  with  various  refrigerants  and  with 
special  machines  using  combination  or  dual  working  mediums.  In 
case  of  the  dual  liquid,  one  of  the  substances  should  be  capable  of 
liquefaction  at  a  comparatively  low  pressure,  at  the  same  time  taking 
the  other  substance  into  solution  by  absorption.  In  some  machines 
of  this  type,  the  refrigerating  agent  is  liquefied  partly  by  absorption 
and  partly  by  mechanical  compression.  A  machine  developed  by 
Johnson  and  Whitelaw  uses  bisulphide  of  carbon  which  is  first  vapor- 
ized and  then,  together  with  air  introduced  by  a  force  pump,  is  passed 
through  chambers  charged  with  oil  where  the  bulk  of  the  moisture 
in  the  gas  is  taken  up  or  absorbed,  provision  being  made  for  extract- 
ing the  moisture  from  the  air  by  passing  it  over  chloride  of  calcium 
on  its  way  to  the  pump.  Pictet's  refrigerating  agent  is  a  combina- 
tion of  carbon  dioxide  and  sulphur  dioxide,  the  latter  constituting 
97  per  cent  of  the  mixture.  This  fluid  gives  a  boiling  point  14  degrees 
F.  lower  than  is  had  with  pure  sulphide  dioxide,  and  its  latent  heat 
is  practically  the  same  as  that  of  this  material. 

In  an  apparatus  designed  to  work  on  the  vacuum  principle,  by 
De  Motay  and  Rossi,  the  refrigerating  agent  is  a  mixture  made  up 
of  common  ether  and  sulphur  dioxide,  known  as  ethylo-sulphurous 
oxide.  At  ordinary  temperatures,  liquid  ether  has  the  power  of  taking 
up,  or  absorbing  sulphur  dioxide,  the  absorption  in  some  cases  being 
as  much  as  300  times  its  own  bulk,  while  the  tension  of  the  vapor 
given  off  from  the  compound  or  dual  liquid  is  below  that  of  the  atmos- 
phere for  a  temperature  of  60°  F.  This  dual  liquid  is  placed  in  the 
refrigerator  and  evaporated  by  reducing  the  pressure  with  air  pumps, 
as  in  the  vacuum  system,  so  that  the  pressure  is  no  greater  than  re- 


REFRIGERATION  57 

quired  to  cause  liquefaction  of  ether.  Owing  to  the  absorption  of 
sulphur  dioxide  by  ether,  the  pump  need  not  have  as  large  capacity 
as  if  ether  alone  were  used,  but  must  necessarily  have  greater  capacity 
than  if  pure  sulphur  dioxide  were  used.  Neither  the  vacuum  system 
nor  the  binary  system  with  dual  liquid  refrigerant  have  come  into 
general  use.  Practically  all  refrigeration  is  done  with  simple  refrig- 
erants. » 

Care  and  Management.*  To  be  successful  in  handling  an  absorp- 
tion plant,  the  man  in  charge  must  be  regular  in  his  habits  and  methods 
and,  above  all,  must  know  his  plant  from  top  to  bottom,  having  the 
location  of  every  valve  and  connection  in  mind.  Regular  inspections 
should  be  made  to  see  if  all  parts  are  in  good  condition  and  if  the 
apparatus  is  performing  its  full  duty.  Gauges  and  thermometers 
with  test  cocks  enable  the  engineer  to  ascertain  this  latter  point. 
There  should  be  a  pressure  gauge  on  the  generator  and  one  on  the 
low-pressure  side.  Some  engineers  prefer  also  to  have  such  a  gauge 
on  the  absorber.  These  gauges  should  have  pipe  connection  with 
shut-off  valves,  so  that  they  can  be  inspected  and  repaired  if  necessary. 
It  is  convenient  to  run  the  pipe  to  a  gauge  board  located  where  readily 
seen,  so  that  the  condition  of  all  parts  as  to  pressure  may  be  seen  at 
a  glance.  Owing  to  the  danger  of  bursting,  some  engineers  prefer  to 
work  their  plants  without  glass  liquid-level  gauges,  especially  on  the 
high-pressure  side.  In  some  cases  this  difficulty  is  overcome  by  using 
special  casings  for  the  glass  tube  and  special  shut-off  valves  that 
close  automatically  in  case  of  a  break.  In  other  cases  the  gauge 
glasses  on  the  high-pressure  side  are  kept  shut  off  except  when  a 
reading  is  desired.  Where  used,  such  gauges  are  placed  on  the 
generator,  the  absorber,  and  the  ammonia  condenser  or  liquid  re- 
ceiver. Test  cocks  are  placed  on  the  generator  and,  in  some  cases, 
on  the  absorber. 

Thermometers  should  be  used  freely  on  all  principal  pipe  lines. 
One  should  be  placed  on  the  ammonia  liquid  line  near  the  expansion 
valve;  another,  in  the  poor  liquor  pipe  near  the  absorber;  while  a 
third  is  connected  direct  to  the  absorber,  a  fourth,  to  the  manifolds 
of  the  bath  coils,  and  a  fifth,  to  the  cooling  water  pipe  near  the  con- 
denser. Instruments  can  also  be  used  to  advantage  on  the  rectifier, 
analyzer,  and  exchanger.  Portable  thermometers,  and  hydrometers 
for  measuring  the  temperature  and  density  of  brine  and  other  liquids, 


REFRIGERATION 


should  be  provided;  while  the  engineer  should  have  indicating  ap- 
paratus for  the  ammonia  and  steam  cylinders,  as  well  as  scales  and 
measuring  vessels  for  performing  rough  tests  in  measuring  coal  and 
water  used,  ice  turned  out,  ammonia  supplied  to  system,  etc.  Two 
forms  of  connections  for  thermometers  placed  on  the  pipe  lines  are 
shown  in  Fig.  10. 

Preliminary  to  charging  and  putting  a  plant  in  operation  it  must 
be  tested  under  pressure  for  leaks.  This  is  done  by  connecting  the 

suction  of  the 
ammonia  pump 
to  a  water  sup- 
ply and  pumping 
water  into  the 
system  until  full 
and  a  pressure  of 
150  pounds  is 
had.  Inspection 
is  then  made  for 
leaks  and,  if  ev- 
erything proves 
tight,  the  pres- 
sure is  increased 
gradually  to  300 
pounds  or  some- 
thing more.  This 
pressure  is  main- 
tained for  at  least  half  an  hour  while  careful  inspection  of  all 
joints  is  made.  While  the  pressure  is  on,  the  valves  on  the  gauge 
piping  connections  are  closed  and  the  gauges  disconnected  and 
cleaned  by  blowing  out.  Drains  are  then  opened  and  the  water 
allowed  to  flow  out  of  all  parts  of  the  system  except  from  the  generator, 
which  is  left  half  full. 

Steam  pressure  of  50  pounds  is  then  turned  on  the  generator  coil, 
which  results  in  a  pressure  of  30  pounds  in  the  generator  as  soon  as  the 
water  is  heated  and  sufficient  steam  made  to  fill  the  high  pressure  side. 
At  this  stage  the  valves  on  the  weak  liquor  pipe  to  the  absorber  are 
opened  and  the  pressure  forces  the  water  from  generator  to  absorber. 
Suction  of  ammonia  pump  is  now  connected  to  absorber,  and  the 


Fig.  10.    Thermometer  Attachments. 


REFRIGERATION  59 

water  and  steam  circulated  through  the  system,  while  the  vent  cocks 
are  left  open  so  that  all  parts  are  thoroughly  cleaned  and  blown  out. 
After  this  has  gone  on  for  an  hour  or  so,  the  pump  is  stopped,  the 
steam  shut  off  the  generator  coil,  and  the  system  allowed  to  cool.  As 
soon  as  steam  stops  issuing  from  vent  cocks,  they  are  closed,  and  the 
stop  valves  separating  the  various  parts  of  the  system  a  re  closed  so  that, 
as  vacuum  is  formed  in  different  parts  by  condensing  steam,  a  leak  in 
one  part  need  not  affect  the  rest  of  the  plant. 

Charging.  With  the  system  under  a  vacuum,  as  after  steaming 
out,  aqua  ammonia  may  be  forced  into  the  generator  and  absorber 
by  atmospheric  pressure.  Otherwise,  the  ammonia  pump  must  be 
used  to  fill  the  two  parts  of  the  system — one  after  the  other.  An 
auxiliary  suction  makes  connection  to  the  pump,  and  the  end  of  the 
suction  pipe  is  inserted  in  the  1^-inch  bung  hole  of  an  aqua  ammonia 
irum  to  within  1  inch  of  the  bottom.  All  valves  on  the  discharge  side 
of  the  pump  are  opened  and  the  ammonia  is  pumped  into  the  system, 
care  being  taken  to  keep  the  drum  as  cool  as  possible.  The  generator 
is  filled  to  the  working  level,  as  shown  by  the  gauge  cocks,  and  the  ab- 
sorber is  filled  to  the  top  of  the  gauge  glass.  The  ammonia  pump  is 
now  connected  with  its  suction  to  the  absorber;  all  valves  are  adjusted 
for  regular  working  conditions  with  steam  admitted  to  the  generator 
coils;  the  ammonia  gas  generated  is  allowed  to  pass  over  to  the  con- 
denser, over  which  cooling  water  is  circulated.  When  the  pressure 
is  about  120  pounds  on  the  high  side,  the  ammonia  pump  is  started 
slowly,  and  the  liquor  level  in  the  absorber  is  gradually  reduced  to  the 
normal  about  mid -height  of  the  gauge  glass.  With  cooling  water  circu- 
lating through  the  absorber  coils  and  the  weak  liquor  cooler,  the 
plant  is  in  full  operation. 

At  least  once  a  day  the  coils  of  the  absorber  should  be  examined 
to  make  sure  that  they  are  clear.  In  case  the  pressure  gets  above  12 
pounds,  attention  should  be  given  the  coils  and  the  expansion  valves. 
The  temperature  at  this  pressure  should  be  between  86  and  90  degrees, 
and  if  it  increases  to  more  than  this  the  supply  of  cooling  water  through 
the  coils  should  be  increased.  Every  two  of  three  days  the  foul  gas 
should  be  burned  off  the  absorber  at  the  purge  cock.  Where  the 
weak  liquor  cooler  is  employed,  care  should  be  taken  to  see  that  the 
coils  are  in  good  condition— this,  in  fact,  applies  to  all  coils  in  the 
plant — so  that  the  liquor  reaches  the  absorber  as  cool  as  possible. 


60  REFRIGERATION 

Once  or  twice  a  week,  and  oftener,  if  necessary,  the  rich  liquor  should 
be  tested  for  density  and  should  show  at  least  26°  Saurae*.  If  run  at 
28°,  the  ammonia  pump  may  be  slowed  down.  In  some  plants  this 
greater  density  can  be  used  to  advantage. 

When  the  quantity  of  liquor  in  the  system  gets  low,  as  shown  by 
the  gauges  on  the  generator  and  absorber,  aqua  ammonia  is  charged 
into  the  system  by  connecting  to  the  absorber;  while,  if  the  liquor  gets 
weak,  anhydrous  ammonia  is  added  by  connecting  the  drum  between 
the  ammonia  receiver  and  the  expansion  valves.  It  is  best  to  place 
the  drum  on  scales  and  to  charge  only  a  part  of  the  ammonia  in  it  at 
one  time.  As  soon  as  the  effect  of  the  amount  charged  is  seen,  more 
can  be  added  if  thought  advisable.  With  proper  working,  the  density 
of  the  weak  liquor  leaving  the  generator  should  not  be  more  than  18 
degrees,  and  if  found  to  be  more  than  this,  the  cause  must  be  removed. 
It  may  be  due  to  running  the  ammonia  pump  too  fast;  but  if  not  this, 
the  trouble  will  be  found  in  the  analyzer  where  one  or  more  pans  will 
probably  be  found  broken. 

To  stop  the  machine,  close  the  steam  valve  to  the  generator, 
allowing  the  ammonia  pump  to  run  until  the  pressure  is  raised  to  150 
pounds,  when  it  is  stopped  and  the  expansion  valves  closed.  Thus 
the  machine  is  left  to  cool  of  its  own  accord,  and  this  is  much  better 
than  cooling  it  quickly.  When,  however,  circumstances  require  that 
the  temperature  be  lowered  rapidly,  the  steam  valve  to  the  generator 
is  closed  and  the  pipe  disconnected  so  as  to  admit  water  to  the  coil, 
through  which  the  circulation  of  water  is  kept  up  until  there  is  no 
apparent  odor  of  ammonia. 

Efficiency  Tests.  It  is  not  the  intention  in  the  brief  space  here 
available  to  give  a  complete  code  of  rules  for  conducting  tests.  Such 
a  course  is  impossible.  For  the  rules  now  recognized  as  standard 
in  this  country,  the  student  must  have  reference  to  the  Proceedings 
of  the  American  Society  of  Mechanical  Engineers.  The  rules  adopted 
by  this  society  for  testing  refrigerating  machines  is  very  complete  and 
elaborate.  Briefly,  it  may  be  said,  that  a  complete  test  must  involve 
every  part  of  the  plant  from  the  coal  pile  to  the  ice  dump,  careful  and 
accurate  measurements  being  made  of  the  fuel  and  water  used,  as  well 
as  of  the  temperatures  in  the  different  parts  of  the  system  and  the 
corresponding  pressures.  A  test  should  be  run  for  at  least  one  week, 
or  long  enough  to  get  all  average  conditions. 


REFRIGERATION  61 

Economy  of  Absorption  Machine.  Dry  gas  governs  the  economy 
of  the  machine  more  than  any  other  factor.  It  was  the  difficulty  in 
getting  dry  gas  with  the  early  machines  that  put  them  out  of  the  race 
with  compression  apparatus  to  such  an  extent  that  they  have  never 
regained  the  lost  ground,  the  compression  system  being  used  in  the 
great  majority  of  plants  to-day.  For  hot  climates  the  absorption 
machine  has  some  advantages;  and  it  is  highly  efficient  for  low  tem- 
peratures, as  required,  for  example,  in  fish  freezing  plants.  Practically 
all  moisture  should  be  eliminated  and  in  no  case  should  more  than  5 
per  cent  be  tolerated.  Owing  to  presence  of  moisture,  many  of  the 
machines  in  operation  must  carry  a  low  back  pressure  with  corre- 
sponding loss  of  economy.  Twelve  pounds  back  pressure  is  the  lower 
limit.  With  perfectly  dry  gas  the  machine  should  be  able  to  carry 
considerably  more  than  this  with  increased  economy.  One  should 
strive  to  have  the  back  pressure  as  high  as  practicable  as,  the  higher 
this  pressure  the  stronger  the  rich  liquor  and  the  less  pumping  required 
per  ton  of  refrigeration  produced.  The  relative  economy  of  the  ab- 
sorption and  compression  systems  is  an  open  question  and  depends 
largely  on  the  local  conditions  of  any  given  case. 

COMPRESSION  SYSTEM 

This  system  dates  from  the  invention  by  Jacob  Perkins,  made 
about  1834,  of  a  machine  operating  on  the  compression  plan  and  using 
a  volatile  liquid  derived  from  the  destructive  distillation  of  caoutchouc. 
Perkins'  machine  was  little  more  than  an  experiment  and  was  never 
used  commercially.  About  1850  Twining  made  improvements  in  the 
apparatus,  using  the  same  principles  as  Perkins,  and  developed  his 
machine  so  that  it  came  into  practical  use  in  one  or  two  eases,  particu- 
larly in  Cleveland,  O.,  where  a  machine  designed  for  2,000  pounds 
of  ice  per  24  hours,  actually  turned  out  1,600  pounds,  and  was  used 
off  and  on  for  three  years.  None  of  the  early  machines  were  much 
in  use  until  the  adoption  of  ether  as  a  refrigerant.  The  successful 
application  of  the  compression  machine  may  be  said  to  date  from  the 
invention  of  the  ether  machine  by  James  Harrison  about  1856.  Sul- 
phuric ether  as  used  in  Harrison's  machine  is  obtained  from  the  action 
of  sulphuric  acid  on  vinous  alcohol.  It  has  a  specific  gravity  of  0.72, 
with  latent  heat  of  vaporization  165,  and  boiling  point  96°  F.  at  atmos- 
pheric pressure.  Various  forms  of  the  ether  machine  were  in  use  for 


62  REFRIGERATION 

a  few  years  following  the  invention  of  Harrison.  Owing,  however, 
to  the  disadvantages  already  mentioned,  it  was  soon  succeeded  by  the 
sulphuric  acid  apparatus,  and  this,  in  turn,  by  the  ammonia  and  car- 
bon dioxide  compression  machines,  as  soon  as  the  absorption  machine 
had  shown  itself  inefficient  and  the  methods  of  iron  manufacture  had 
been  developed  sufficiently  to  construct  machines  of  strength  neces- 
sary in  handling  ammonia.  Since  1860  to  1865,  the  ammonia  com- 
pression machine  has  practically  held  the  field,  though  in  the  last 
decade  it  is  meeting  considerable  competition  by  the  absorption 
systems  as  improved  to  operate  with  dry  gas  and  the  compression 
machines  using  carbon  dioxi;le. 


Fig.  11.    Primitive  Refrigerating  Apparatus. 

Operating  Principle.  As  already  shown,  production  of  refrigera- 
tion in  latent-heat  machines  depends  on  the  principle  of  heat  absorp- 
tion or  change  to  latent  form  when  a  volatile  liquid  evaporates.  This 
is  shown  in  Fig.  11,  where  the  small  vessel,  at  the  top  of  the  illustra- 
tion, containing  a  volatile  liquid,  and  set  in  a  second  vessel  containing 
a  liquid  to  be  frozen,  represents  the  simplest  possible  form  of  refriger- 
ating apparatus.  If  volatile  liquids  could  be  obtained  at  nominal  cost, 
no  other  refrigerating  apparatus  than  that  shown  would  be  necessary, 
though  it  would  be  convenient  to  connect  the  supply  drum  of  the 
liquid  to  the  evaporating  vessel  by  pipe  so  as  to  give  a  continuous  flow 
of  the  volatile  liquid  to  take  the  place  of  that  evaporated  and  dissipated 


REFRIGERATION  63 

in  the  atmosphere.  The  simplest  system  would  thus  be  made  up 
of  an  evaporator  arranged  to  cool  any  substance  desired  and  a 
receptacle  for  the  refrigerant  with  a  connecting  pipe  between  hav- 
ing an  expansion  valve  to  regulate  the  flow  of  the  liquid  to  the  evap- 
orator. 

As  the  cost  of  ammonia,  for  example,  is  about  $200  per  ton  of 
refrigerating  capacity,  where  wasted,  as  in  Fig.  11,  it  is  evident  that 
some  means  of  conserving  the  refrigerant  and  using  it  over  must  be 
adopted.  To  do  this,  the  heat  absorbed  by  it  in  evaporating  must  be 
removed;  and  it  is  this  removal  that  makes  necessary  the  use  of 
machinery  in  a  refrigerating  plant.  In  such  an  establishment  there 
are  three  processes — the  gas  is  first  reduced  in  volume  by  a  com- 
pressor in  which  expended  work  takes  the  form  of  heat  and  raises 
the  temperature  of  the  gas;  this  hot  gas  is  then  passed  to  a  condenser 
where  the  heat  is  given  up  to  cooling  water  and  the  gas  restored  to  the 
liquid  form,  in  which  it  passes  to  the  third  stage  of  the  process,  to  be 
evaporated  in  such  a  manner  as  to  absorb  additional  heat. 

Fig.  12  shows  the  complete  compression  plant  in  its  simplest 
form.  The  supply  drum  is  connected  to  the  evaporator,  which  in  turn 
is  connected  to  the  suction  of  the  compressor  that  discharges  to  the 
condenser,  from  which  the  liquefied  refrigerant  passes  to  the  supply 
drum.  From  the  discharge  pipe  E  of  the  compressor,  the  ammonia 
passes  to  the  oil  separator  F  and  goes  thence  to  the  condenser  C, 
made  up  of  a  series  of  pipes  over  which  water  flows  to  take  up  the  heat 
in  the  gas.  Liquid  anhydrous  ammonia  from  the  bottom  of  the  con- 
denser passes  through  the  pipe  H  to  the  drum  I,  which  is  known  as 
the  ammonia  receiver.  As  there  is  some  loss  of  heat  in  cooling  the 
liquid  ammonia  from  the  temperature  of  the  condenser  or  ammonia 
receiver  to  that  of  the  evaporator,  it  is  seen  that  the  three  stages  of 
compression,  condensation,  and  expansion  as  applied  in  commercial 
refrigerating  machines,  although  making  a  closed  operating  cycle,  do 
not  make  a  complete  reversible  cycle.  The  cost  of  machinery  neces- 
sary to  utilize  work  by  expansion  in  cooling  the  liquid  ammonia  being 
more  than  the  value  of  the  work  performed,  this  cooling  is  done  at 
the  expense  of  the  refrigeration  of  the  system.  It  is  then  in  order  to 
see  how  the  apparatus  for  carrying  out  the  three  essential  processes  is 
constructed  and  to  ^tudy  the  proportion  and  combination  of  the  dif- 
ferent parts  in  making  up  the  refrigerating  plant. 


64  REFRIGERATION 

* 

Compressors.  Compressors  may  be  divided  into  two  principal 
classes,  single  and  double-acting;  and  each  class  subdivided  into  the 
vertical  and  horizontal.  They  are  of  the  vertical  type  if  single-acting, 
and  of  both  vertical  and  horizontal  if  double-acting,  although  the 


Fig.  12.    Diagram  of  a  Complete  Compression  Plant. 

majority  of  the  double-acting  are  of  the  horizontal  type.  Machines 
may  also  be  classed  according  to  the  mode  of  driving,  whether  by 
engine  connected  direct  or  by  belt,  or  by  motor  drive  with  geared  or 
belted  connection.  The  engine  may  be  used  vertical  or  horizontal, 
and  within  this  classification  comes  almost  any  machine  of  modern 
build.  In  all  except  the  smallest  machines,  and  in  some  designs  for 
extremely  large  units,  the  engines  are  direct-connected  to  the  same 
crank-shaft  as  the  compressors.  Either  simple  or  compound  engines 
may  be  used,  and  if  there  is  enough  cooling  water  the  engines  may  be 


REFRIGERATION  65 

run  condensing.  In  some  eases  the  connecting  rod  of  the  engine  is 
attached  to  the  same  crank  pin  as  that  of  the  compressor  and  in  others, 
to  a  separate  crank  on  the  same  shaft.  One  form  of  the  horizontal 
machine  has  the  engine  connected  to  a  crank  at  one  end  of  the  shaft, 
while  the  other  end  has  a  crank  arranged  to  drive  two  single  or  double- 
acting  horizontal  compressors.  Another  arrangement  has  the  engine 
connected  to  the  middle  of  the  crank-shaft  so  as  to  drive  two  com- 
pressors of  either  the  horizontal  or  vertical,  single-  or  double-acting 
type.  All  of  the  various  arrangements  use  fly-wheels  to  give  steady 
working,  these  being  placed  in  various  ways  according  to  the  disposal 
of  the  other  parts  of  the  machine.  Where  compound  engines  are  em- 
ployed, each  cylinder  usually  drives  its  own  compressor  cylinder,  the 
connecting  rods  of  steam  and  compressor  cylinders  being  attached  to 
a  common  crank  pin,  with  the  fly-wheel  at  the  middle  of  the  shaft. 
In  the  tandem  machine,  having  the  ammonia  and  steam  cylinders  in 
line  on  a  common  center  with  their  pistons  on  the  same  rod,  a  connect- 
ing rod  drives  a  crank-shaft  on  which  are  two  fly-wheels  placed  at 
the  ends. 

In  comparing  the  single  and  double-acting  compressors,  it  is 
seen  at  once  that  the  stuffing-box — a  vital  part — can  be  kept  tight 
easily  in  the  single-acting  machine,  where  it  is  subjected  only  to  the 
comparatively  low  pressure  of  the  suction  gas  instead  of  the  pressure 
of  the  condenser  which  ranges  from  125  pounds,  upward.  On  the 
other  hand,  a  double-acting  compressor  is  more  economical  because, 
at  each  revolution  of  the  crank-shaft,  it  deals  with  almost  twice  as 
much  gas  as  a  single-acting  machine  of  the  same  diameter  and  stroke. 
With  the  exception  of  the  extra  friction  resulting  from  the  neces- 
sarily tighter  stuffing-box  gland  of  the  double-acting  machine,  the 
friction  of  the  two  machines  is  the  same.  With  improved  stuffing- 
box  construction,  the  friction  is  much  reduced,  and  in  a  box  properly 
adjusted  may  be  little,  if  any  more,  than  for  the  single-acting  ma- 
chine, particularly  taking  into  account  the  friction  of  the  two  boxes 
necessary  for  a  machine  of  this  type  to  have  the  same  capacity  as 
the  double-acting  equipment. 

Altogether  it  is  estimated  that,  as  against  a  machine  having  two 
single-acting  gas  compressors,  the  double-acting  machine  will  save 
about  one-eighth  the  total  power  necessary  to  compress  a  given  amount 
of  gas.  Also  less  material  is  required  for  the  single  cylinder  used  in 


66  REFRIGERATION 

the  double-acting  machine,  but  this  is  partly  offset  by  the  extra  care  and 
expense  necessary  to  construct  the  latter  type  of  machine.  It  is  more 
difficult  to  adjust  the  piston  for  clearance  in  the  double-acting  ma- 
chine but  with  proper  care  it  can  be  done  correctly.  An  advantage 
of  two  single-acting  compressors  is  the  fact,  that  in  case  of  accident 
to  one  of  the  cylinders,  the  other  may  be  kept  going  at  increased  speed 
to  keep  the  temperature  of  the  coolers  down  so  that  the  pipes  will 
not  drip.  For  this  and  other  reasons  it  is  customary  to  use  two  cylin- 
ders where  the  single-acting  machine  is  employed  and  the  cranks  are 
set  opposite  or  at  180  degrees  to  one  another,  so  that  one  compressor 
is  filling,  and  one  compressing  and  charging,  at  each  half  revolution 
of  the  crank-shaft. 

There  is  some  difference  of  opinion  as  to  the  relative  merits  of 
the  vertical  and  horizontal  types  of  machines,  but  in  respect  of  uni- 
form wear  of  the  moving  parts  it  is  plain  that  the  vertical  machine 
has  the  advantage.  As  little  oil  as  possible  should  be  used  in  refrig- 
erating machines  and  prevention  of  undue  wear  is  an  important  con- 
sideration. Vertical  machines  are  not  subject  to  bottom  wear  of  the 
pistons  as  are  horizontal  compressors  in  which  the  weight  of  the  piston 
is  supported  by  the  lower  half  of  the  cylinder  wall.  When  the  piston 
is  near  the  crank  end  of  the  stroke,  part  of  the  weight  is  supported 
by  the  stuffing-box  glands,  resulting  in  unequal  wear.  In  the  vertical 
compressor  the  valves  and  piston  work  up  and  down,  so  that  the  wear 
is  equal  in  all  directions  and  there  is  little  friction.  Owing  to  the 
fact  that  the  vertical  machine  is  comparatively  expensive  to  build 
and  care  for  properly,  there  are  greater  fixed  charges  and  more  depre- 
ciation with  this  type  of  machine.  As  to  space  occupied  by  the  two 
forms  of  machine,  there  is  little  difference,  the  choice  depending 
principally  on  whether  vertical  or  horizontal  space  is  more  valuable. 

Essentials  in  Compressors.  Owing  to  the  extreme  tenuity  of 
gases  used  in  refrigerating,  considerable  care  must  be  taken  in  design- 
ing and  operating  compressors  if  the  maximum  possible  efficiency 
is  to  be  had.  Handling  ammonia,  for  example,  is  quite  another 
matter  from  handling  steam,  and  a  joint  that  will  hold  steam  at  high 
pressure  may  be  a  perfect  sieve  for  leakage  when  it  comes  to  ammonia. 
This  is  even  more  true  with  carbon  dioxide  with  which  the  pressures 
are  much  higher  than  in  machines  using  ammonia.  Provision  should 
be  made  to  remove  the  heat  of  compression,  and  the  clearance  should 


REFRIGERATION  67 

be  made  as  small  as  possible,  consistent  with  safe  working.  Any  gas 
left  in  the  clearance  spaces  expands  on  the  return  stroke  of  the  piston 
and  prevents  the  cylinder  filling  properly  with  the  low-pressure  gas, 
so  that  there  is  a  large  loss  in  efficiency.  Stuffing-boxes,  valves,  and 
pistons  should  be  kept  tight  to  prevent  leakage  of  the  gas  and  yet 
should  not  be  so  tight  as  to  cause  undue  friction.  This  calls  for  great 
care  in  adjusting  and  lubricating  the  machine,  methods  of  doing 
which  will  be  discussed  more  in  detail  later. 

The  piston  and  valves  are  the  heart  of  the  compressor  and  prac- 
tically all  troubles  in  operation  may  be  traced  to  one  or  the  other 
of  these  parts,  when  it  will  be  found  that  lubrication  is  imperfect  or 
that  they  are  out  of  adjustment  for  the  prevailing  conditions  of  pres- 
sure and  speed  of  operation.  In  most  designs  of  ammonia  com- 
pressors, the  suction  and  discharge  valves  operate  in  cages,  the  valves 
on  one  end  of  a  cylinder  being  usually  mounted  in  a  common  casing 
which  acts  as  the  cylinder  head  and  may  be  removed  bodily.  In 
the  double-acting  machines,  there  being  no  provision  forwater  jacket 
on  the  ends  of  the  cylinder,  the  valves  are  accessible  singly  if  desired, 
and  in  some  designs,  as  the  Triumph  for  example,  the  construction 
is  such  that  the  adjustment  for  spring  tension  in  the  valves  may  be 
made  while  the  machine  is  in  operation. 

Compressor  Valves.  There  must  of  necessity  be  a  gas-tight 
joint  between  the  valve  cage  and  the  cylinder  head,  which  may  be 
made  in  a  number  of  ways.  In  one  method,  a  square  recess  or 
shoulder  is  cut  in  the  head  and  a  corresponding  shoulder  is  cut  on  the 
face  of  the  valve  cage.  A  lead  gasket  about  $  inch  in  thickness  is 
placed  in  the  shoulder  of  the  head  and  the  cage  adjusted  with  set 
screws  provided  for  the  purpose  until  in  proper  position.  This  makes 
a  durable  joint  except  where  the  openings  at  the  facing  surfaces  of  the 
shoulders  are  such  that  the  lead  is  pressed  out — a  disadvantage  of 
lead  as  a  gasket  material.  When  this  happens,  the  gasket  is  gone  and 
a  leak  develops  before  the  engineer  is  aware  that  trouble  is  brewing. 
Another  objection  to  a  lead  gasket  is  that  it  compresses  and  knits  into 
the  interstices  between  the  cage  and  the  cylinder  head,  so  that  it  is 
often  impossible  to  remove  a  valve  or  the  cage  without  the  aid  of  a 
chain  block  and  tackle. 

Another  form  of  gasket  for  the  valve  cage,  but  one  not  popular 
on  account  of  lack  of  confidence  in  its  permanency,  is  common  lamp 


68  REFRIGERATION 

or  candle  wicking  saturated  with  oil  and  wound  tightly  or  smoothly 
in  the  corner  against  the  shoulder  on  the  cage.  It  is  put  in  place  and 
fully  compressed  by  pulling  down  on  the  valve  cap  until  the  cage  is 
in  the  desired  position.  Recently  engineers  have  come  to  the  con- 
clusion that  any  form  of  gasket  joint  is  a  nuisance  for  joining  the 
cylinder  head  or  valve  cage  on  an  ammonia  compressor  cylinder,  so 
that  the  ground  joint  has  come  into  use,  the  facing  surfaces  being 
ground  to  an  absolute  smooth  surface,  before  the  parts  are  joined. 
This  is  the  type  of  joint  that  has  been  employed  for  some  years,  with 
gratifying  results,  in  pipe  work  on  vessels  where  highly  superheated 
steam  is  used.  The  joint  made  is  perfectly  tight  and  there  is  no 
factor  of  depreciation  as  by  gasket  becoming  worn  and  ineffective, 
but  great  care  must  be  taken  in  overhauling  not  to  scar  the  surfaces, 
when  they  would  have  to  be  reground  at  considerable  expense. 

Assuming  that  the  joint  between  the  valve  cage  and  the  cylinder 
head  has  been  made  gas-tight,  it  is  next  of  importance  to  see  that  the 
valve  makes  a  perfect  joint  in  closing  against  the  seat  in  the  cage. 
This  is  the  more  difficult  of  the  two  propositions  for  the  valve,  being 
in  constant  motion  under  severe  conditions  of  changing  pressure,  is 
likely  to  act  erratically  and,  in  some  cases,  pounds  itself  and  the  seat 
to  such  an  extent  that  the  surfaces  have  to  be  reground  to  a  joint. 
From  this  it  is  evident  that  the  best  material  obtainable  should  be 
used  in  the  valves  and  seats  and  in  the  valve  stems,  which  should  be 
immune  from  breakage  as  far  as  possible.  The  valve  stem  must  fit 
the  guides  in  the  cage  as  closely  as  possible  and  still  allow  free  move- 
ment, and  the  seat  between  the  valve  disk  and  cage  (preferably  mac'e 
at  an  angle  of  45  degrees)  must  be  machined  and  ground  to  accurate 
dimensions  and  surface.  Having  made  it  impossible  for  the  gas  to 
pass  the  cage  and  valves,  means  must  be  provided  for  closing  the 
valves  at  the  proper  time  to  prevent  loss,  as  a  valve  that  is  slow  in 
reaching  its  seat  causes  double  damage  in  loss  of  efficiency  and  in 
irregular  action  on  the  other  parts  of  the  machine.  Springs  are  ordi- 
narily used  to  operate  the  suction  and  discharge  valves  (as  already 
mentioned  in  discussing  unbalanced  valve  action),  these  being  placed 
between  the  cage  and  a  washer  on  the  end  of  the  stem  in  the  case  of 
the  suction  valves,  and  between  the  casing  and  a  similar  washer 
placed  near  the  middle  of  the  stem  in  the  case  of  the  discharge  valves. 
Nuts  on  the  end  of  the  stems  hold  the  springs  and  washers  in  position 


REFRIGERATION 


and  afford  means  of  adjusting  the  spring  tension,  there  being  two 
nuts  on  each  stem  so  that  they  may  be  locked  at  any  point  desired. 
Buffer  springs  are  used  to  give  steady  action  in  some  valves  but  it  is 
considered  better  practice  to  use  a  dashpot  chamber  on  the  valve  stem 
for  this  purpose,  as  the  working  of  a  valve  having  such  chamber  is 
more  regular  and  noiseless,  there  being  little  or  no  hammering  action 
on  the  seats. 

Suction  and  discharge  valves  should  be  constructed  to  give  ample 


Fig.  13a.    Triumph  Suction  Valve. 


Pig.  135.    Triumph  Discharge  Valve. 


area  of  opening,  with  lightness  of  moving  parts,  quick  seating,  and 
noiseless  action.  As  compressors  must  be  constructed  with  little 
clearance,  it  is  important  that  the  valves  be  so  made  that  they  cannot 
fall  into  the  cylinder  in  case  of  accidental  breakage.  Space  does  not 
permit  discussion  of  the  various  forms  of  compressor  valves  on  the 
market,  but  a  good  idea  of  construction  for  double-acting  compressors 
may  be  had  by  reference  to  Fig.  13,  which  shows  the  suction  and  dis- 
charge valves  as  constructed  by  the  Triumph  Ice  Machine  Co.  The 
discharge  valve  is  shown  at  the  right,  where  it  is  seen  that  the  cross-sec- 
tion of  the  stem  is  smallest  above  the  safety  collar  so  that  any  possible 


70 


REFRIGERATION 


break  will  occur  above  this  collar  and  the  valve  be  prevented  from 
falling  into  the  cylinder.  This  collar,  it  is  noted,  also  works  in  a 
dashpot  that  steadies  the  operation  of  the  valve.  The  tension  and 
buffer  springs  with  the  lock  nuts  for  adjustment  are  seen  at  the  upper 
end  of  the  valve  stems,  and  the  valve  cages  as  a  whole  are  held  in 
position  against  ground  joints  at  top  and  bottom,  by  set  screws,  so 


Fig.  14.    Featherstone  Balanced  Suction  Valves. 


that  gas  cannot  escape  to  the  inside  of  the  outer  casing,  which  is  used 
for  protection  only  and  may  be  removed  freely  for  adjustment  of  the 
valve.  Fig.  14  shows  at  the  left  the  construction  of  valve  made 
by  the  Featherstone  Foundry  and  Machine  Co.  for  use  in  single- 
acting  machines.  The  manner  in  which  the  valve  is  set  in  po- 
sition in  the  safety  head  of  the  compressor  is  shown  at  the  right 
of  the  figure.  Various  constructions  and  arrangements  of  valves 
are  adopted  by  the  different  manufacturers;  but  after  under- 
standing the  valves  illustrated  in  Figs.  13  and  14,  the  student  will 
be  able  to  handle  any  special  valve  with  which  he  comes  in  con- 
tact. 


REFRIGERATION  71 

Valve  Operation.  With  any  type  of  valve,  it  is  required  that  the 
gas  be  admitted  to  the  cylinder  as  the  piston  recedes  from  the  end  of 
the  cylinder  in  which  the  valve  is  located.  The  valve  must  close  as 
the  piston  reaches  the  opposite  end  of  the  stroke  at  the  instant  the 
crank  is  passing  over  the  center.  If  the  spring  is  stronger  than  neces- 
sary, the  gas  must  exert  a  certain  pressure  to  overcome  its  action  and 
the  cylinder  will  not  be  filled  to  the  limit  of  its  capacity.  Also  in 
closing,  the  strong  spring  drives  the  valve  against  its  seat  with  consider- 
able force,  making  a  disagreeable  noise  that  means  excessive  wear. 
Considerable  skill  and  experience  are  required  to  obtain  the  best 
results  with  compressor  valves,  but  with  good  judgment  and  a  few 
trials  most  of  the  imperfections  in  adjustment  can  be  overcome. 
Generally  the  closing  spring  of  the  suction  valve  should  not  be  stronger 
than  necessary  to  close  the  valve  when  held  in  the  hand  in  the  position 
— either  vertical  or  at  an  angle — it  naturally  occupies  in  the  cage  of 
the  machine.  By  taking  the  valves  and  cages  in  the  hands  and  press- 
ing down  on  the  top  of  the  stem  with  one  of  the  fingers,  it  will  readily 
be  seen  when  the  springs  are  of  proper  strength  to  effect  closure. 

Discharge  valves  operate  in  the  reverse  direction  to  that  of  the 
suction  valves.  As  the  piston  advances  on  the  compression  stroke, 
the  pressure  of  the  gas  in  the  cylinder  increases  until  it  is  as  high  as 
that  in  the  ammonia  condenser  plus  the  pressure  required  to  over- 
come the  tension  of  the  springs  on  the  discharge  valve.  At  this  pres- 
sure the  valve  opens  and  the  gas  is  discharged  into  the  pipe  leading  to 
the  condenser,  the  valve  remaining  open  until  the  crank  passes  the 
center  corresponding  to  the  end  of  the  cylinder  from  which  the  gas 
is  being  discharged.  At  this  instant,  the  valve  should  close  if  it  is 
of  proper  proportions  and  the  tension  of  the  spring  is  what  it  should 
be.  This  tension  should,  be  no  more  than  necessary  to  make  the 
valve  close  promptly  and  easily  as  the  crank  passes  over  the  center, 
any  greater  tension  increasing  the  loss  by  unbalanced  pressure  on  the 
faces  of  the  valve.  The  suction  valve  should  open  at  the  same  instant 
that  the  discharge  valve  closes,  that  is — as  the  crank  is  passing  over 
the  center  nearest  the  end  of  the  cylinder  in  which  the  valve  is 
placed. 

It  will  be  noticed  that  the  suction  valve  opens  and  closes  while 
the  piston  is  practically  without  motion,  but  the  discharge  valve  opens 
while  the  piston  is  nearly  at  its  maximum,  and  closes  while  the  piston 


72 


REFRIGERATION 


is  at  its  minimum  speed.  From  this  it  will  be  apparent  that  the 
thrust  or  effort  on  the  discharge  valve  is  much  greater  than  on  the  inlet, 
that  is,  in  an  upward  or  outward  direction;  hence  the  device  for  ar- 
resting the  upward  motion  of  the  valve  must  be  more  effective  than 
the  other.  Also  the  valve  must  close  in  a  shorter  space  of  time  because 
the  great  pressure  above  the  valve  would  cause  it  to  fall  with  consider- 
able force  were  it  not  to  reach  its  seat  while  the  piston  was  still  at  the 
top  of  its  travel,  and  the  pressure  above  and  below  equal.  Should  the 
piston  begin  its  return  or  downward  stroke  before  the  valve  closes  it 
would  have  the  condensing  pressure  above  and  the  inlet  pressure 

TABLE  XVI 
Cubic  Feet  of  Qas  to  be  Pumped  per  Ton 


W     . 

°^ 

TEMPERATURE  OF   THE  GAS  IN  DEGREES  F. 

jjs 

IIP 

65°          70°          75°          80°          85°          90°          95°        100°        105° 

g« 

s*S 

CORRESPONDING  CONDENSER  PRESSURE  (GAUGE)  LBS.  PER  Sq.  IN. 

ll 

Ijl 

103        115         127         139         153        168          184         200       218 

G.  PRES. 

' 

-27° 

1 

7.22 

7.3 

7.37 

7.46 

7.54 

7.62 

7.70 

7.79 

7.88 

-20° 

4 

5.84 

5.9 

5.96 

6.03 

6.09 

6.16 

6.23 

6.30 

6.43 

-15° 

6 

5.35 

5.4 

5.46 

5.52 

5.58 

5.64 

5.70 

5.77 

5.83 

-10° 

9 

4.66 

4.73 

4.76 

4.81 

4.86 

4.91 

4.97 

5.05 

5.08 

-  5° 

13 

4.09 

4.12 

4.17 

4.21 

4.25 

4.30 

4.35 

4.40 

4.44 

0° 

16 

3.59 

3.63 

3.66 

3.70 

3.74 

3.78 

3.83 

3.87 

3.91 

5° 

20 

3.20 

3.24 

3.27 

3.30 

3.34 

3.38 

3.41 

3.45 

8.49 

10° 

24 

2.87 

2.9 

2.93 

2.96 

2.99 

3.02 

3.06 

3.09 

3.12 

15° 

28 

2.59 

2.61 

2.65 

2.68 

2.71 

2.73 

2.76 

2.80 

2.82 

20° 

33 

2.31 

2.34 

2.36 

2.38 

2.41 

2.44 

2.46 

2.49 

2.51 

25° 

39 

2.06 

2.08 

2.10 

2.12 

2.15 

2.17 

2.20 

2.22 

2.24 

30° 

45 

1.85 

1.89 

1.89 

1.91 

1.93 

1.95 

1.97 

2.00 

2.01 

35° 

51 

1.70 

1.72 

1.74 

1.76 

1.77 

1.79 

1.81 

1.83 

1.85 

below,  a  difference  of  from  150  to  175  pounds.  This  pressure  would 
cause  it  to  seat  with  an  excessive  blow  which  would  soon  cause  its 
destruction,  and  also  cause  the  escape  of  a  portion  of  the  com- 
pressed gas  into  the  compressor  resulting  in  great  loss  in  efficiency  of 
the  machine.  . 

Valve  Proportions.  Knowing  the  amount  of  gas  that  must  be 
compressed  and  passed  through  the  valves  as  well  as  the  velocity  at 
which  it  is  advisable  to  force  the  gas  through  the  machine,  it  is  possible 
to  determine  the  size  of  valve  opening.  Table  XVI  gives  the  number 


REFRIGERATION  73 

of  cubic  feet  of  gas  that  must  be  pumped  per  minute  at  different  suc- 
tion and  condenser  pressures  to  give  1  ton  of  refrigeration  in  24  hours. 
It  is  customary  to  base  the  area  of  the  suction  valve  on  a  velocity  of 
4,000  feet  a  minute  and  that  of  the  discharge  valve  on  6,000  feet. 
Taking,  then,  the  case  of  a  10-ton  compressor  with  back  pressure  of 
13  pounds  and  condenser  pressure  of  184  pounds,  it  is  seen,  from 
the  "table,  that  4.35  X  10  cubic  feet  of  gas  must  be  pumped  per 
minute.  Since  the  amount  of  gas  pumped  is  found  by  multi- 
plying the  area  of  the  valve  opening  by  the  velocity  of  the  gas, 
it  is  evident  that  the  area  can  be  found  by  dividing  the  quan- 
tity that  must  be  pumped  by  the  velocity,  the  units  of  measurement 
being  the  same,  i.  e.  feet,  throughout.  Thus  43.5  -r-  4,000  = 
0.010875  sq.  ft.  or,  1.566  sq.  in.  corresponding  to  a  diameter  of 
1.47197  in.  For  the  discharge  valve,  the  area  is  43.5  V  6,000  = 
0.00725  sq.  ft.  or,  1.044  sq.  in.  This  means  a  diameter  of  1.15253 
inches. 

Valves  proportioned  in  this  way  have  proved  satisfactory  at 
piston  speeds  of  from  270  to  400  feet  a  minute  and  from  40  to  100 
revolutions.  The  York  Manufacturing  Co.  has  made  tests  to  deter- 
mine the  effect  of  velocity  of  flow  through  the  valves  on  the  efficiency 
of  the  machine  and  the  power  required  to  compress  a  given  amount 
of  gas.  As  a  result,  this  company  has  found  that  the  area  of  the  dis- 
charge valve  opening  may  be  made  somewhat  less  than  that  corre- 
sponding to  6,000  feet  a  minute  velocity  of  gas,  without  loss  of 
efficiency.  In  fact  the  experiments  show  that  up  to  a  velocity  of 
about  9,000  feet  a  minute,  the  efficiency  increases,  more  gas  being 
pumped  without  increase  in  power  in  proportion  to  work  done.  The 
same  experiments  show  that  it  is  better  to  have  a  lower  velocity 
through  the  suction  valve.  The  velocity  for  best  results  is  about 
3,000  feet,  which  calls  for  a  considerably  larger  "valve  opening  on  the 
suction  than  figured  on  a  basis  of  4,000  feet  a  minute. 

Compressor  Piston.  Having  provided  the  inlet  and  outlet  valves 
with  proper  opening  and  closing  devices  and  made  them  capable  of 
retaining  the  gas  passing  them,  a  piston  for  compressing  the  gas  and 
discharging  it  from  the  compressor  must  be  provided.  For  the  vertical 
type  of  single-acting  compressor  in  which  both  inlet  valves  are  in  the 
upper  compressor  head,  the  piston  is  best  made  as  a  ribbed  disk  with 
a  hub  at  the  center  for  the  piston  rod  and  a  periphery  of  sufficient 


74 


REFRIGERATION 


width  to  be  grooved  for  the  necessary  snap  rings.     Three  to  five  of 
these  rings  are  generally  used. 

In  double-acting  machines  it  is  customary  to  use  the  spherical 
form  of  piston  as  will  be  seen  in  discussing  this  form  of  compressor. 
Fig.  15  illustrates  the  simplest  form  of  this  type  of  piston,  A  being 
the  cast  head,  B  the  snap  rings,  and  C  the  piston  rod.  The  surface  is 
faced  square  with  the  bore  of  the  hub,  and  the  rod  forced  in  and  riveted 
over,  filling  the  small  counterbore  provided  for  this  purpose.  The 
cast  head  and  rod  having  been  previously  roughed  out,  the  piston  is 
now  finished  in  its  assembled  condition.  The  rod  is  made  parallel 


Fig.  15.    Disk  Type  of  Piston. 


and  true  to  gauge  and  threaded  to  fit  the  crosshead.  The  grooves  are 
turned  for  the  snap  rings,  which  are  made  slightly  larger  than  the  bore 
of  the  compressor.  A  diagonal  cut  is  made  through  one  side  and 
enough  of  the  ring  is  cut  out  to  allow  it  to  slip  into  the  cylinder  without 
binding.  It  is  then  scraped  on  its  sides  until  it  fits  accurately  the 
groove  in^  the  piston.  It  is  also  well  to  turn  a  small  half-round  oil 
groove  in  the  outer  face  of  the  piston  between  each  ring  ,  which 
gathers  and  retains  a  portion  of  the  oil  used  for  lubrication,  thus 
increasing  the  efficiency  of  the  piston  and  collecting  dust  or  scale 
and  lessening  the  liability  of  cutting  of  the  cylinder  due  to  any  of  the 
usual  causes. 

The  piston  rod  requires  special  care  both  in  workmanship  and 
material.     In  order  to  be  effective  it  must  be  true  from  end  to  end; 


REFRIGERATION 


75 


and  to  be  lasting  under  the  variety  of  conditions  which  it  operates,  it 
should  be  of  a  good  grade  of  tool  steel.  The  end  which  is  usually 
made  to  screw  into  the  crosshead  is  turned  somewhat  smaller,  usually 
from  %  to  |  inch  in  diameter,  than  the  portion  passing  through  the 
packing  or  stuffing  box,  principally  to  allow  of  re-turning  or  truing  up 
the  rod  when  it  becomes  worn,  and  also  to  allow  it  to  pass  through  the 
stuffing  box.  After  the  rod  is  screwed  into  the  crosshead  it  is 
secured  and  locked  with  a  nut  to  prevent  turning.  The  nut  also 
allows  the  position  of  the  piston  to  be  changed  to  compensate  for 
wear 'on  the  different  parts  of  the  machine  by  simply  loosening  the 
lock  nut  and  turning  the  piston  and  the  rod  in  or  outof  the  cross- 
head. 

Stuffing  Box.     The  stuffing  box  of  the  compressor  is  one  of  the 
most  difficult  parts  to  keep  in  proper  order.     This  is  owing  principally 


Fig.  16.    Type  of  Double- Acting  Stuffing  Box. 

to  one  of  two  causes :  not  being  in  line  with  the  crosshead  guide  or  bore 
of  the  compressor,  or,  the  great  difference  of  temperature  to  which  it 
is  subjected  owing  to  the  possible  changes  taking  place  in  the  evapora- 
tor. However,  with  the  compressor  crosshead  guides  and  stuffing 
box  in  per-'ect  alignment,  and  a  constant  pressure  or  temperature  on 
the  evaporating  side,  it  is  a  simple  matter  to  keep  the  stuffing  box 
tight  and  in  good  condition.  If,  however,  either  of  these  conditions 
is  changed,  it  becomes  practically  impossible  to  do  so.  With  single- 
acting  compressors  the  stuffing  box  is  a  simple  gland  with  any  good 
ammonia  packing. 

One  form  of  box  use  1  in  the  double-acting  compressor  is  shown 
in  Fig.  16,  this  being  the  construction  employed  by  the  Featherstone 


76 


REFRIGERATION 


Foundry  and  Machine  Co.  A,  B,  C,  D,  E,  and  F,  indicate  composi- 
tion split  packing  rings,  while  Q,  R,  S,  U,  V,  and  W  denote  pure  tin 
rings  of  an  inside  diameter  TV  inch  larger  than  that  of  the  piston 
rod.  These  tin  rings  should  not  be  split.  At  J  is  a  lantern  forming 
an  oil  reservoir,  the  oil  being  supplied  by  pipe  at  the  connection 
marked  K.  This  pipe  is  connected  to  the  oil  trap  and,  as  the  passage 
is  always  open,  oil  is  forced  into  the  stuffing  box  by  the  high  pressure 
of  the  gas  in  the  trap,  so  that  any  little  oil  carried  into  the  cylinder 
by  the  rod  is  instantly  replaced  and  the  lantern  kept  full.  A  second 
lantern  L  has  connection  to  the  suction  line  at  M,  so  that  any  gas  that 
may  have  escaped  the  rings  C,  D,  E,  and  F  is  drawn  back.  With 
this  arrangement  packing  rings  A  and  B  have  to  withstand  only  the 
suction  pressure.  The  stuffing-box  gland  N  has  a  chamber  that  is 
supplied  with  oil  through  the  connection  0  by  a  small  rotary  oil  pump 
operated  from  the  main  shaft.  A 
secondary  gland  P  retains  the  oil  in 
the  gland  and  should  be  adjusted  just 
tight  enough  for  this  purpose.  G,  H, 
and  I  are  points  of  contact  with  the 
rod  and  are  babbitted  to  an  exact  fit. 
In  case  the  rod  should  have  to  be 
turned  down  or  when  this  babbitt  is 
worn,  for  any  cause,  so  that  it  does 
not  fit  exact,  it  should  be  renewed. 
The  general  principles  involved  in 
this  stuffing  box  are  used  in  more  or 
less  modified  form  by  all  the  leading 
manufacturers'  of  double-acting  ma- 
chines. 

Water  Jacket.  In  the  vertical  single-acting  type  of  compressor 
it  is  usual  to  provide  a  water  jacket,  which  may  be  cast  in  combination 
with  the  compressor  cylinder  or  made  of  some  sheet  metal  secured  to 
an  angle,  which  is  bolted  to  a  flange  cast  on  the  cylinder.  It  is  usual 
to  have  this  water  jacket  start  at  about  the  middle  of  the  compressor 
(or  a  little  below,  as  shown  in  Fig.  17)  and  extend  enough  above  to 
cover  the  compressor  heads,  valves,  and  bonnets  with  water;  the  prin- 
cipal object  of  which  is  to  keep  these  parts  at  a  normal  temperature 
and  thereby  improve  the  operation  as  well  as  protect  the  joints  against 


Fig.  17.    Jacket  of  Single- Acting 
Compressor. 


REFRIGERATION  77 

the  excessive  heat  which  would  be  generated  by  the  continued  com- 
pression. It  is  also  an  advantage  in  the  operation  of  the  plant,  since 
by  reducing  the  temperature  in  the  compressor  and  adjacent  parts, 
the  compressor  is  filled  with  gas  of  a  greater  density.  Also  the  heat 
extracted  or  taken  up  by  the  water  at  this  point  is  a  certain  portion 
of  the  work  performed  in  the  condenser  and  therefore  not  a  waste. 
Double-acting  compressors  may  or  may  not  use  the  water  jacket,  but 
in  those  where  it  is  used  the  water  surrounds  the  cylinder  only,  there 
being  no  means  of  circulating  water  around  the  heads,  where  the  valves 
are  placed  in  their  casings.  In  such  machines  the  cylinder  is  made  of 
special  close-grained  steel  and  is  forced  into  the  frame  of  the  machine 
under  hydraulic  pressure,  thus  forming  an  annular  space  between  it 
and  the  frame  in  which  the  cooling  water  is  circulated,  being 
admitted  near  the  bottom  of  the  space  at  one  side  and  drawn 
off  at  the  top.  In  the  wet  compression  machines  and  in  those 
using  a  liquid  oil  base,  it  is  not  considered  necessary  to  use  a 
jacket,  but  the  latter  of  these  types  of  machines  is  now  going 
out  of  use,  owing  to  the  complications  incident  to  keeping  the  oil 
out  of  the  piping  of  a  refrigerating  plant  where  it  interferes  with  the 
proper  transfer  of  heat. 

In  the  operation  of  the  plant  it  is  well  to  have  plenty  of  water 
flow  through  the  jackets,  as  the  cooler  the  compressors  are  kept  the 
better;  but  in  plants  in  which  water  is  scarce  the  quantity  may  be 
reduced  correspondingly  until  the  overflow  is  upwards  of  100  degrees 
F.  In  extreme  cases  of  shortage  of  water  the  overflow  water  from  the 
ammonia  condenser  is  sometimes  used  on  the  jackets — that  is,  the 
entire  amount  of  available  water  is  delivered  to  the  condenser,  and  a 
supply  from  the  catch  pan  (if  it  be  an  atmospheric  type)  is  taken  for 
the  water  jackets,  in  which  case  a  greater  quantity  may  be  used  but  at 
a  higher  temperature.  In  the  vertical  single-acting  machine  it  is 
customary  to  admit  the  water  through  the  flange  forming  the  bottom  of 
the  water  jacket  and  to  connect  the  overflow  near  the  top  into  a  stand 
pipe  which  is  connected  at  its  lower  end  through  the  flange  to  a  system 
of  pipes  to  take  it  away.  To  prevent  condensation  on  the  outer  sur- 
face of  the  jacket,  and  to  present  a  more  pleasing  appearance,  it  is  fre- 
quently lagged  with  hardwood  strips  and  bound  with  finished  brass  or 
nickel-plated  bands.  It  is  well  to  have  a  washout  connection  from 
each  jacket. 


78 


REFRIGERATION 


Lubrication.  Excessive  lubrication  is  an  objection,  owing  to  the 
insulating  effect  upon  the  surfaces  of  the  condensing  and  evaporating 
system.  Therefore  it  is  well  to  feed  to  the  compressors  as  little  as  is 
consistent  with  the  operation  of  the  machinery.  A  proper  separating 
device  should  be  located  in  the  discharge  pipe  from  the  compressor 
to  the  condenser.  To  properly  admit,  or  feed  the  lubricant  to  the 
compressors,  sight  feed  lubricators  should  be  provided,  by  which 
the  amount  may  be  determined  and  regulated.  These  may  be  of 


Fig.  18.    System  of  Lubrication. 


the  reservoir  type,  or  better  still  the  droppers,  fed  from  a  large  reser- 
voir through  a  pipe,  and  which  may  be  filled  by  a  hand  pump  when 
necessary,  Fig.  18.  Owing  to  the  action  of  ammonia  on  animal 
or  vegetable  oils,  other  than  these  must  be  used  as  lubricants  for  the 
compressor.  The  principal  oil  for  this  purpose  (and  when  obtained 
pure,  a  very  good  one)  is  the  West  Virginia  Natural  Lubricating  Oil 
or  Mount  Farm,  which  is  a  dark-colored  oil  not  affected  by  the 
action  of  the  ammonia  or  the  low  temperature  of  the  evaporator. 


REFRIGERATION  79 

Of  late  years  the  oil  refining  companies  have  put  on  the  market  a 
light-colored  oil  which  appears  to  give  good  results  for  the  purpose. 
Care  should  Le  used,  however,  in  the  selection;  and  oil  should  not 
be  used  unless  it  is  of  the  proper  grade,  as  serious  results  follow  the 
use  of  ir/crior  oils.  The  usual  result  is  the  gumming  of  the  com- 
pressors and  valves  or  the  saponifying  under  the  action  of  the  am- 
monia through  the  system. 


REFRIGERATION 

PART  II 


COMMERCIAL  MACHINES 

No  attempt  is  made  here  to  catalogue  all  the  many  refrigerating 
machines  on  the  market,  but  some  of  the  leading  points  of  typical 
machines  of  the  principal  makes  will  be  pointed  out  briefly.  Thus  the 
student  can  get  an  insight  into  the  general  principles  of  design  and 
arrangement  as  applied  to  refrigerating  machines,  and  can  supple- 
ment the  descriptions  here  given  by  detail  study  of  manufacturers' 
catalogues,  by  which  means  a  detailed  knowledge  of  any  particular 
machine  or  group  of  machines  may  be  had . 

Horizontal  Double=acting.  Triumph.  ]£ig.  19  shows  in  a 
striking  manner  the  simple  and  massive  construction  of  this  machine. 
One  continuous  bed  plate  gives  a  firm  support  for  the  compressor 
cylinder,  the  crosshead,  and  the  crankshaft.  The  crosshead  is  of 
compact  form  and  is  supported  on  shoes.  These  have  large  bearing 
surfaces  \vith  an  arrangement  to  take  up  wear  by  wedge  and  screw 
adjustment.  The  crosshead  pin  is  a  ground  taper  fit,  and  is  held  in 
position  by  a  bolted  disk.  Owing  to  the  piston  being  screwed  into  the 
crosshead  and  fastened  with  a  lock  nut,  it  is  a  simple  matter  to  ad- 
just the  clearance  for  both  ends  of  the  cylinder.  The  connecting  rod 
is  made  from  a  heavy  steel  forging  and  is  provided  with  a  bronze  box 
at  the  crosshead  end,  while  a  babbitt- lined  brass  box  is  used  on  the 
crank  pin,  both  bt>xes  being  fitted  with  wedge  and  screw  adjustments. 

Something  has  already  been  said  of  the  valve  adjustment  which 
is  made  by  means  of  a  nut  on  the  stem,  the  tension  of  the  cushion 
spring  being  regulated  by  turning  the  nut  after  the  lock  nuts  have 
been  loosened.  On  the  collar  under  the  adjusting  nut  is  a  secondary 
collar  with  which  the  working  spring  is  adjusted,  and  these  two  collars 
are  held  in  their  correct  positions  by  keepers.  This  adjustment 


82 


REFRIGERATION 


feature  of  the  valves  has  an  important  bearing  on  the  economy  cf  the 
compressor,  as  it  is  evident  that  the  same  pressures  cannot  be  used 
under  varying  conditions  with  maximum  economy  at  all  times. 

Particular  attention  is  directed  to  the  stuffing  box  of  this  machine, 
which  is  divided  into  three  parts  separated  by  two  cages,  which  are  of 
spider  frame  construction  as  shown  in  the  figure.  One  of  the  cages 
forms  a  relief  chamber  from  which  any  gas  that  may  leak  past  the  first 
packing  is  returned  to  the  suction  manifold,  while  the  other  serves 


Fig.  19.    Section  of  Triumph  (Compressor. 

as  an  oil  reservoir  that  keeps  the  rod  and  packing  well  lubricated. 
Oil  is  circulated  through  the  gland  by  means  of  a  small  power  pump 
driven  from  the  shaft  of  the  machine.  The  oil  is  drawn  from  a  cham- 
ber provided  in  the  base  of  the  machine  under  the  cylinder.  Thus 
there  is  a  continuous  circulation  of  oil  and  it  is  necessary  to  pump 
against  only  the  suction  pressure.  Fig.  20  shows  an  outside  view  of 
a  70-ton  Triumph  unit,  in  which  the  stuffing-box  connections  and 
lubricating  apparatus  are  shown  more  in  detail.  It  is  noted  that  all 
the  bolts  of  the  gland  are  connected  by  inside  gear  so  that  in  turning 
one  nut,  uniform  adjustment  is  given  to  all.  Thus  there  can  be  no 
trouble  from  cocking  the  gland  by  unequal  adjustment. 


REFRIGERATION  83 

Linde.  This  machine  is  similar  in  many  respects  to  the  Triumph, 
and  is  manufactured  by  the  Linde  Refrigerating  Co.,  New  York,  with 
the  usual  heavy-duty  type  of  frame  and  bored  guides  for  the  cross- 
head.  The  piston  is  of  the  spherical  form  used  in  all  the  best  hori- 
zontal machines  of  the  double-acting  type,  and  enables  the  valves  to 
be  set  close  in  the  head  so  as  to  reduce  clearance  to  a  minimum.  To 
facilitate  handling,  each  valve  is  made  so  as  to  form  virtually  a  single 


Fig.  20.    Exterior  Triumph  Machine  Showing  Stuffing-Box  Arrangement. 

part  with  its  seat,  enabling  the  valve  and  seat -to  be  removed  together 
with  the  same  labor  that  would  be  necessary  to  remove  either  sep- 
arately. The  valve-seat  casting  rests  on  the  cylinder  head  and  is 
held  in  place  by  the  valve-stem  guide  which  is  secured  in  position  by 
the  cap  or  bonnet.  With  the  bonnet  oil,  the  valve  and  all  its  parts 
can  be  removed  practically  as  one  piece  and  without  disturbing  any 
part  of  the  machine. 

Two  self-expanding  rings  make  the  piston  tight,  and  strength  is 
given  by  heavy  reinforcing  ribs.  The  stuffing-box  packing  may  be 
seen  readily  in  Fig.  21,  which  is  a  sectional  view  of  the  cylinder  of  this 
machine.  It  will  be  seen  that  the  arrangement  is  similar  to  the  other 


84 


REFRIGERATION 


double-acting  stuffing  boxes  already  described,    the  outer  packing 
having  to  withstand  only  the  pressure  of  the  suction  gas.     Particular 


Fig.  21.    Sectional  View  of  the  Cylinder  of  the  Linde  Compressor. 

note  should  be  made  of  the  fact  that  there  is  no  water  jacket  on  the 
cylinder  of  the  Linde  machine.  The  distinctive  feature  of  this  ma- 
chine is  its  operation  on  the  wet  system,  where  the  cylinder  is  kept  cool 


Fig.  22.    Longitudinal  Sectional  Elevation  of  York  Machine. 

by  the  injection  of  a  small  amount  of  liquid  ammonia  at  the  beginning 
of  the  compression  stroke;  or,  arranging  the  system  so  that  a  small 
part  of  the  liquid  is  not  evaporated  and  goes  back  to  the  compressor. 


REFRIGERATION 


85 


Vertical  Compressors.  Although  some  manufacturers  make  a 
vertical  double-acting  machine,  the  most  notable  being  that  of  the 
De  La  Vergne  Machine  Co.,  the  great  majority  of  such  machines  are 
single-acting.  The  discussion  will  therefore  be  confined  to  this  type 
of  apparatus. 


Fig.  23.    Cross-Sectional  Elevation  of  the  York  Machine. 

York.  Figs.  22  and  23  show  longitudinal  and  cross-sectional 
views  of  the  York  machine  direct-connected  to  its  steam  engine.  It 
consists  of  two  single-acting  compressor  cylinders  mounted  on  vertical 
/1-frames  and  driven  from  a  Corliss  engine  of  the  horizontal  type. 
A  fly-wheel  is  mounted  on  the  middle  of  the  crank-shaft,  and  a  crank 
on  each  end  of  the  shaft  drives  the  compressor  cylinders,  the  cranks 
being  set  180  degrees  apart  for  reasons  already  mentioned.  The  con- 


REFRIGERATION 


iiecting  rod  of  the  engine  is  attached  to  one  of  the  cranks,  as  shown  in 
the  illustrations.  Gas  enters  the  cylinders  through  valves  at  the  bot- 
tom underneath  the  piston  and,  on  the  down  stroke  of  the  piston,  is 
forced  through  the  valve  in  the  piston  to  the  space  above  so  as 
to  fill  the  cylinder.  On  the  return  or  compression  stroke  of  the 
piston  the  gas  is  compressed  and,  at  the  end  of  the  stroke, 

is  forced  out  through 
the  valve  in  the  up- 
per head,  going  thence 
through  the  pipe  connec- 
tion to  the  condenser. 
The  upper  head  itself, 
being  of  the  safety  type, 
may  be  considered  as 
one  huge  valve,  as  in  case 
anything  should  get  in 
the  cylinder,  or  the  clear- 
ance become  too  small 
for  any  reason,  the  piston 
may  strike  the  head  with- 
out doing  damage.  The 
effect  is  similar  to  lifting 
the  head  against  the  ac- 
tion of  heavy  buffer 
springs,  shown  in  the  il- 
lustration, and  allowing 
the  charge  in  the  cylin- 
der to  pass  over  to  the 
condenser  by  the  regular 
connections. 

Great  Lakes.  In  this  machine,  which  is  made  by  the  Great  Lakes 
Engineering  Works,  there  is  no  valve  in  the  piston.  Separate  suction 
and  discharge  valves  are  provided  in  the  head  of  the  machine,  as 
shown  in  Fig.  24,  there  being  two  valves  of  each  kind.  Sight-feed 
lubricators  are  provided,  as  shown,  and  the  cylinder  has  a  specially 
arranged  water-jacket  around  the  upper  end.  One  of  the  special 
features  is  the  arrangement  of  the  suction  and  discharge  passages, 
which  are  connected  to  the  piping  system  of  the  plant  by  a  system 


Fig.  24.    Cylinder  of  Great  Lakes  Refrigerating 
Machine. 


REFRIGERATION 


S7 


of  manifolds  and  by-passes  that  permit  of  handling  the  gas  in  any 
way  desired.  Like  the  York  machine  this  compressor  is  single-acting, 
gas  being  drawn  in  through  the  right-hand  valve,  on  the  down-stroke, 
as  seen  in  the  illustration,  and  discharged  through  the  other  valve 
on  the  up-stroke.  The  two  suction  and  the  two  discharge  valves 
work,  each  pair,  as  one  valve,  they  being  made  in  pairs  owing  to  the 
fact  that  there  is  not  room  enough  within  the  head  to  give  the  proper 
diameter  for  the  necessary  valve  opening  for  a  single-suction  and  a 
single-discharge  valve. 

Carbon  Dioxide   Machines.     Owing  to  the  difficulty  in  getting 
sound  castings  suitable  to  withstand  the  pressure  necessary  to  liquefy 


Fig.  25.    Sectional  View  of  Cylinder  of  Carbon-Dioxide  Machine.    Suction  Passages  are  so 
arranged  that  coal  gas  passes  around  cylinder  before  entering  suction  valve. 

carbon  dioxide,  manufacturers  in  the  United  States  have  largely 
adopted  soft  forged  steel  for  the  cylinders.  With  summer  temperature 
of  water  the  pressure  may  be  as  much  as  1,000  pounds  or  more,  and 
it  is  seen  at  once  that  the  cylinders  and  piping  must  be  very  strong. 
The  diameter  of  the  gas  cylinder  must  be  small  as  compared  with 
that  of  the  steam  cylinder.  In  some  cases  the  compressors  are  made 
to  compress  the  gas  in  stages.  The  gas  leaves  the  first  cylinder  at  a 
pressure  of  from  400  to  600  pounds  per  square  inch,  and  is  cooled 
before  entering  the  second  cylinder  where  it  is  compressed  to  the  final 
pressure.  Owing  to  the  difficulty  in  keeping  stuffing  boxes  tight 
with  the  high  pressures,  compressors  are  usually  made  single-acting, 
but  some  manufacturers  have  been  successful  with  the  double-acting 
machine. 


88 


REFRIGERATION 


Fig.  26.    Small  Vertical  Carbon-Dioxide  Machine. 


90  REFRIGERATION 

Ordinarily  the  length  of  the  stroke  should  be  about  four  times 
the  diameter  of  the  cylinder,  and,  if  the  piston  is  to  be  kept  tight,  it 
should  be  at  least  two  and  one-half  times  the  cylinder  diameter.  Fig. 
25  is  a  sectional  view  of  the  typical  cylinder  in  which  it  will  be  seen 
that  the  suction  passages  are  arranged  to  pass  the  cool  gas  around 
the  cylinder  before  entering  it.  Although  the  suction  valves  are  usu- 
ally placed  in  a  horizontal  position,  they  are  easily  closed  by  light 
springs  as  they  are  small  and  have  little  inertia.  Guides  are  used  to 
keep  the  valves  in  line  with  the  seat;  and  the  discharge  valves,  being 
set  vertical,  easily  come  to  a  true  seating.  Suction  valves  should 
have  an  area  of  about  one-half  that  of  the  piston  and  the  area  of  the 
discharge  valves  should  be  about  one-seventh  that  of  the  piston. 

Owing  to  the  limited  space  on  the  crank  end  of  the  cylinder,  it 
is  usually  necessary  to  have  two  suction  valves  for  this  end.  For  the 
discharge  valves,  the  seats  should  be  beveled  at  from  70  to  80  degrees, 
while  for  the  suction  valves  the  seats  should  be  beveled  from  60  to  75 
degrees;  and  the  seats  for  both  valves  are  from  0.1  to  0.12  of  the  disk 
diameter  in  width.  On  the  suction  valve  the  lift  should  be  about 
0.33  of  the  disk  diameter  while  that  for  the  discharge  valve  should  be 
about  0.28  of  the  diameter.  Spring  tension  is  8  or  9  pounds  on  the 
suction  and  10  or  11  pounds  on  the  discharge  valve.  Stuffing  boxes 
are  made  on  the  same  general  principles  as  those  for  the  double- 
acting  ammonia  compressors,  bearing  in  mind  that  the  greater  pres- 
sures call  for  more  compartments.  Cup  leather  packings  are  used 
except  for  the  outer  packing  which  is  merely  a  wiper  for  the  rod. 
Small  machines  are  usually  made  vertical,  Fig.  26,  which  shows  a 
direct-connected  vertical  unit  built  by  the  Brown-Cochrane  Co. 
Above  2  tons  capacity,  the  machines  are  usually  made  horizontal,  as 
shown  in  Fig.  27,  which  is  an  illustration  of  the  double-acting  com- 
pressor built  by  Kroeschell  Bros.,  Chicago,  111. 

Small  Refrigerating  Plants.  In  recent  years  large  consumers 
of  ice  have  created  a  demand  for  small  plants  to  be  used  on  their 
premises  and  thus  do  away  with  the  "ice  man."  As  a  result,  machines 
are  now  made  in  capacities  ranging  upward  from  |-ton  refrigerating 
duty.  Such  apparatus  is  used  for  a  number  of  purposes.  Where 
the  consumer  can  obtain  cheap  electric  power  and  is  able  to  stand 
the  first  cost  of  the  apparatus,  there  is  some  economy  in  operating  a 
refrigerating  plant  by  electricity.  Where  electric  power  is  not  avail- 


REFRIGERATION 


91 


able  and  a  special  engine  equipment  must  be  used — gasoline  engines 
as  a  rule — there  will  be  no  economy,  and  the  matter  of  installing 
such  a  plant  must  be  decided  on  other  grounds.  Where  temperatures 
below  32°  are  required,  the  installing  of  such  a  plant  is  a  necessity. 
Hospitals,  restaurants,  cafes,  and  saloons  use  the  small  refrigerating 
plant  to  advantage  because  they  can  keep  the  coolers  drier,  colder, 


Exterior  of  Brunswick  Machine. 


and  more  sanitary  than  by  the  use  of  ice.  Residences  and  country 
clubs  use  such  machines,  owing  to  the  fact  that  ice  cannot  be  obtained 
readily.  Where  it  is  a  mere  question  of  refrigeration  of  cooler  boxes 
there  is  an  economy  in  using  the  refrigeration  direct  instead  of  melting 
ice.  The  machine  thus  used  gives  about  twice  as  much  cooling  for 
a  given  amount  of  power  expended  as  is  secured  by  using  the  ice 
made  by  refrigeration. 

As  the  small  machine  must  be  operated  by  servants  and  other 
unskilled  persons,  it  is  made  as  near  automatic  as  possible,  this  being 
particularly  the  case  with  the  machines  designed  for  household  use. 


92 


REFRIGERATION 


In  the  larger  hotels  and  clubs  the  machine  will  be  looked  after  by  the 
engineer  of  the  steam  plant,  and  for  machines  above  1  ton  refrigerating 
duty,  it  is  generally  sufficient  to  have  a  reliable  source  of  water  supply 
and  a  thermostat  in  the  cooler  to  regulate  the  operation  of  the  motor. 
Arrangements  should  be  made  so  that  the  power  and  water  are  turned 
off  or  on  simultaneously.  Lubrication  can  be  looked  after  by  the 
attendant,  but  for  machines  smaller  than  1  ton,  as  used  in  residences, 
it  is  advisable  to  have  automatic  lubricating  devices  and,  in  fact,  have 
the  whole  machine  practically  take  care  of  itself, 

Fig.  28  is  an  exterior  view  of  the  complete  Brunswick  refrigera- 
ting machine  made  in  New  Brunswick,  N.  J.,  in  sizes  of  200  pounds 


Fig.  29.    Construction  of  Brunswick  Compressor. 

to  10  tons  refrigerating  duty  or  half  as  much  ice-making  capacity. 
Power  is  furnished  by  a  motor  belted  to  the  band  wheel  seen  in  the 
illustration  at  the  right-hand  end  of  the  shaft.  The  compressor  is 
entirely  self-contained  in  an  enclosed  crank  case,  which  contains  oil 
for  lubricating  purposes.  An  idea  of  the  construction  may  be  had 
from  the  sectional  line  drawings  in  Fig.  29.  The  machine  is  single- 
acting,  the  suction  and  discharge  valves  being  of  special  design  and 
made  of  steel,  with  the  suction  valve  carried  on  the  discharge  valve  and 
seating  on  its  face.  This  construction  makes  it  possible  to  have  the 


REFRIGERATION  93 

discharge  valve  the  full  diameter  of  the  cylinder  so  that  it  becomes  a 
lifting  head  similar  to  the  safety  heads  of  large  single-acting  machines. 
Thus,  there  is  no  clearance  and  all  the  gas  in  the  cylinder  is  forced 
out  at  each  stroke,  the  piston,  in  fact,  passing  beyond  the  discharge 
port  in  the  side  of  the  cylinder  and  at  once  shutting  off  the  port  so  that 
there  can  be  no  back  slip  of  gas.  As  the  piston  reverses,  it  is  followed 
by  the  discharge  valve,  which  rests  on  its  upper  end,  and  as  this  valve 
comes  to  its  seat  with  a  slight  impact  there  is  no  chance  for  the  suction 
valve,  which  seats  on  its  face,  to  get  stuck  and  not  open  promptly. 
The  lift  of  the  suction  valve  is  limited  by  a  nut  on  the  stem;  but  the 
discharge  valve  may  lift  as  much  as  necessary  to  pass  any  obstruction 
that  may  get  into  the  cylinder.  Other  details  of  the  construction  are 
made  plain  by  the  illustration  which  shows  the  eccentric  (used  instead 
of  a  crank  on  the  sha^t),  and  the  arrangements  made  for  lubrication. 
There  are  a  number  of  automatic  and  semi-automatic  machines  on 
the  market,  in  all  of  which  the  arrangements  are  more  or  less  similar, 
the  smallest  units  being  self-contained  with  all  parts  mounted  on  a 
common  base. 

COMPRESSOR  LOSSES 

Having  described  the  compressor  and  its  parts,  let  us  take  up  the 
losses  clue  to  the  improper  working  or  assembling  of  the  parts  of  the 
machine,  before  proceeding  with  the  description  of  the  rest  of  the  plant. 
As  has  been  stated  in  a  general  way,  the  economy  of  the  compressor 
lies  in  its  filling  at  the  nearest  possible  point  to  the  evaporating  pres- 
sure, and  then  compressing  and  discharging  at  the  lowest  possible 
pressure,  as  much  of  the  entire  contents  of  the  cylinder  as  possible. 
If  the  compressor  piston  does  not  travel  close  to  the  upper  end — of  a 
single-acting  machine — or  the  machine  has  excessive  clearance,the  com- 
pressed gas  remaining  in  the  cylinder  re-expands  on  the  downward 
stroke  of  the  piston,  and  the  gas  from  the  evaporator  will  not  be  taken 
into  the  compressor  until  the  pressure  falls  to,  or  slightly  below,  this 
point,  and  the  loss  due  to  this  fault  is  equal  to  the  quantity  of  gas 
thus  prevented  from  entering  the  compressor  plus  the  friction  of  the 
machine  while  compressing  the  portion  of  the  gas  thus  expanding. 

If  we  make  a  full  discharge  of  the  gas  and  there  is  a  leak}'  outlet 
valve  in  the  compressor,  the  escape  and  re-expansion  into  the  com- 
pressor affects  not  only  the  intake  of  the  gas  at  the  beginning  of  the 


94  REFRIGERATION 

return  stroke,  but  continues  to  affect  the  amount  of  incoming  gas 
during  the  entire  stroke  and  the  capacity  of  the  machine  will  be  corre- 
spondingly reduced.  If  the  inlet  valve  is  leaky  or  a  particle  of  scale 
or  dirt  becomes  lodged  on  its  seat,  as  the  piston  moves  upward  the 
portion  of  the  gas  which  may  escape  during  the  period  of  compression 
is  forced  back  to  the  evaporator  and  a  corresponding  loss  is  the  result. 
A  piston  which  does  not  fit  the  compressor,  faulty  piston  rings,  or  a 
compressor  which  has  become  cut  or  worn  to  the  point  of  allowing 
the  escape  of  gas  between  the  cylinder  and  piston  has  the  same  effect 
as  the  ill  conditioned  suction  valve.  The  loss  due  to  leaky  or  defec- 
tive cylinders,  joints,  or  stuffing  boxes,  are  not  included  under  this 
head,  as  these  more  generally  effect  the  loss  of  the  material  than  the 
efficiency  of  the  compressor. 

AMMONIA  CONDENSERS 

The  ammonia  condenser,  or  liquefier,  as  briefly  stated  in  the 
description  of  the  system,  is  that  portion  of  the  plant  in  which  the 
gas  from  the  evaporator,  having  been  compressed  to  a  certain  point, 
is  cooled  by  water  and  thereby  deprived  of  the  heat  which  it  took  up 
during  evaporation;  consequently  it  is  reduced  to  its  initial  state, 
that  is —  liquid  anhydrous  ammonia.  Condensers  for  other  refriger- 
ants are  constructed  in  the  same  general  way  as  those  for  ammonia, 
due  regard  being  had  to  the  pressures  to  be  carried.  Let  us  consider 
the  general  principles  governing  the  action  before  describing  the 
types. 

On  account  of  its  duty  having  been  performed,  the  ammonia 
as  it  leaves  the  evaporating  coils  is  a  gas  at  low  temperature,  usually 
5°  to  10°  below  that  of  the  brine,  or  other  body  upon  which  it  has 
been  doing  duty,  yet  it  is  laden  with  a  certain  amount  of  heat,  although 
at  a  temperature  not  ordinarily  expressed  by  that  term.  It  is  a  well- 
known  fact  that  we  cannot  obtain  a  refrigerating  agent  which  can 
absorb  heat  from  a  body  colder  than  itself,  and  it  is  therefore  necessary 
to  bring  the  temperature  of  the  ammonia  gas  to  a  point  at  which  the 
flow  of  heat  from  the  one  to  the  other  will  take  place.  This  is  done 
by  withdrawing  part  of  the  heat  in  the  ammonia  in  the  following 
manner:  The  cold  gas  is  compressed  until  its  pressure  reaches  such 
a  point  that  at  ordinary  temperatures  it  will  condense  to  liquid  form ; 
as  it  leaves  the  compressor  it  is  very  hot  because  of  the  fact  that  it 


REFRIGERATION  95 

still  contains  nearly  all  of  the  heat  it  had  when  it  left'  the  evaporator, 
in  only  a  small  portion  of  the  space  occupied  before.  Thus  when 
it  reaches  the  condenser  it  is  much  warmer  than  the  cooling  water  and 
will  readily  give  up  its  heat  to  the  cold  water — so  much  that  its  latent 
heat  is  absorbed  by  the  water  and  it  condenses  into  anhydrous  am- 
monia. 

The  temperature  of  water  if  pumped  from  surface  streams  will 
average  about  60°  F.,  and  since  we  cannot  expect  to  get  the  ammonia 
any  colder  than  this,  it  must  be  compressed  until  the  boiling  point 
corresponding  to  the  pressure  obtained  is  at  about  75°  F.  In  Table 
XII,  p.  31,  we  find  that  this  temperature  corresponds  to  a  pressure  of 
141.22  pounds  per  square  inch  (absolute),  or  126.52  pounds  per 
square  inch  (gauge). 

Thus  if  the  gas  is  compressed  until  the  gauge  reads  126.52  and 
then  passed  into  a  condenser  where  the  temperature  of  the  water  is  less 
than  75°  F.,  the  water  will  absorb  the  latent  heat  and  we  have  accom- 
plished our  object  which  was  to  remove  some  of  the  heat  contained 
in  the  ammonia.  In  this  condition  it  is  drained  from  the  condenser 
into  the  ammonia  receiver  to  again  repeat  the  cycle  of  operation. 

The  forms  of  condensers  may  be  divided  into  three  classes — the 
submerged,  the  atmospheric,  and  the  double-pipe.  Of  each  of  these 
classes  a  number  of  different  types  and  constructions  are  in  use.  To 
illustrate  the  general  principles,  however,  it  is  only  necessary  to  pre- 
sent one  of  each  type. 

Submerged  Condenser.  The  submerged  condenser  consists  of 
a  round  or  rectangular  tank  with  a  series  of  spiral  or  flat  coils  within, 
joined  to  headers  at  the  top  and  bottom  with  proper  ammonia  unions. 
In  Fig.  30  is  shown  a  sectional  elevation  of  a  popular  type  of  sub- 
merged condenser.  A  wrought  iron  or  steel  tank  A  is  formed  by  plates 
from  T\  to  T6T  inch  thick,  of  the  necessary  dimensions  to  contain  the 
coils,  and  sufficiently  braced  around  the  top  and  sides  to  prevent  bulg- 
ing when  filled  with  water.  A  series  of  welded  zigzag  pipe  coils  B  are 
placed  in  the  tank  and  joined  to  headers  C  with  ammonia  unions  D. 
The  ammonia  gas  enters  the  top  header  through  the  pipe  E,  and  an 
outlet  for  the  liquefied  ammonia  is  provided  at  F  with  a  proper  stop 
valve.  Water  is  discharged  or  admitted  to  the  tank  at  or  near  the 
bottom  and  overflows  at  outlet  M.  It  will  be  seen  that  in  this  type 
of  condenser  a  complete  reverse  flow  of  the  current  is  effected,,  the 


96 


REFRIGERATION 


gas  entering  at  the  top  and  the  liquid  leaving  at  the  bottom,  while 
the  water  enters  at  the  bottom  and  leaves  at  the  top.  This  brings 
the  cold  water  in  contact  with  the  cool  gas,  and  the  warm  water  in 
contact  with  the  incoming  or  discharged  gas  from  the  compressor, 
thereby  presenting  the  ideal  condition  for  properly  condensing  am- 
monia. 

Owing  to  the  necessarily  large  spaces  between  the  coils  and  the 
distance  between  the  bent  pipes,  the  portion  of  water  coming  in  contact 
with  the  surface  of  the  pipes  must  be  small  compared  with  the  total 
amount  passing  through;  it  is,  therefore,  uneconomical  as  regards 
amount  of  water  used.  With  water  containing  a  large  amount  of  float- 
ing impurities  the  deposit  on  the  coils  is  considerable  and  not  easily 


Fig.  30.    Submerged  Condenser. 

removed  owing  to  the  limited  space  between  the  coils;  and  further- 
more, the  dimensions  of  the  tank  necessary  to  contain  the  requisite 
amount  of  pipe  for  a  plant  of  considerable  size  is  so  great  and  its 
weight,  when  equipped  with  coils  and  filled  with  water,  requires  such 
a  strong  support,  that  its  use  is  now  limited  to  certain  requirements 
and  localities. 

A  better  shape  for  a  condenser  of  this  type  is  one  of  considerable 
height  or  depth,  rather  than  low  and  broad.  This  is  owing  to  the 
fact  that  the  greater  length  of  travel  of  the  water  and  gas  in  opposite 
directions,  the  greater  the  economy.  The  number  of  coils  used  should 
be  such  that  the  combined  internal  area  of  the  pipes  equals  or  ex- 
ceeds the  area  of  the  discharge  pipe  from  the  compressor.  The  circular 


REFRIGERATION  97 

submerged  condenser  is  similar  to  the  above  described  except  that 
the  tank  is  circular  and  the  coils  bent  spirally. 

In  the  circular  type  of  submerged  condenser  the  pipes  are  1^  to 
2  inches  in  diameter,  and  the  separate  coils  are  made  in  lengths  up  to 
350  feet.  A  number  of  coils  are  used  in  a  single  condenser,  the  in- 
lets and  outlets  being  connected  to  manifolds  with  valves  provided 
to  shut  off  any  individual  coil.  Where  the  water  comes  to  the  con- 
denser at  70°  and  leaves  at  80°  —  a  range  of  10  degrees  —  about  40 
square  feet  of  condensing  surface,  corresponding  to  64  running  feet 
of  2-inch  pipe  or  90  feet  of  l|-inch  pipe  are  allowed  per  ton  of  refrig- 
eration. Less  surface  than  this  means  excessive  condensing  pressure. 
Siebel  gives  the  following  empirical  formula  for  calculating  the  square 
feet  of  cooling  surface  F  required  in  submerged  condensers: 


m(t-t'} 

In  this  formula,  h  =  the  heat  of  vaporization  of  1  pound  of  ammonia 
at  the  temperature  of  the  condenser;  k  —  the  amount  of  ammonia  pass- 
ing through  the  condenser  in  one  minute;  m  =  0.5  =  the  number 
of  heat  units  transferred  per  minute  per  square  foot  of  iron  surface 
where  the  pipe  contains  ammonia  vapor  and  is  cooled  by  water;  t  = 
the  temperature  of  the  ammonia  in  the  coils;  t'  =  the  mean  tem- 
perature of  the  inflowing  and  outflowing  cooling  water. 

The  heat  taken  up  by  the  ammonia,  in  producing  refrigeration, 
added  to  that  corresponding  to  the  work  done  on  the  ammonia  in  the 
compressor,  less  any  heat  expended  in  superheating  the  gas,  is  equal 
theoretically  to  the  heat  of  vaporization  of  ammonia  at  the  tempera- 
ture of  the  condenser  and  is  the  amount  of  heat  that  must  be  re- 
moved by  the  cooling  water.  This  then  gives  a  gauge  on  the  amount 
of  cooling  water  that  should  be  used  in  the  plant.  For  finding  the 
number  of  pounds  A  of  cooling  water,  Siebel  gives  the  formula  : 

MX  60 

A—T=r 

in  which  the  notation  is  the  same  as  in  the  formula  above,  except  that 
t  is  the  temperature  of  the  outgoing  cooling  water,  and  If  that  of  the 
incoming  water.  The  result  is  converted  into  gallons  by  dividing 
by  the  factor  8.33.  Usually  from  f  to  3  gallons  of  water  are  required 
per  minute  per  ton  of  refrigeration  in  24  hours. 


98 


REFRIGERATION 


Atmospheric  Condenser.  This  type  of  condenser  most  gener- 
ally used  is  made  of  straight  lengths  of  2-inch  extra  strong,  or  special 
pipe,  usually  20  feet  long,  screwed,  or  screwed  and  soldered  into  steel 
return  bends  about  3^-inch  centers  and  usually  from  eighteen  to 


twenty-four  pipes  high.  The  coil  is  supported  on  cast  or  wrought 
iron  stands  and  placed  within  a  catch  pan,  or  on  a  water-tight  floor, 
having  a  proper  waste  water  outlet,  and  supplied  with  one  of  the 
several  means  of  supplying  the  cooling  water  over  their  surfaces. 


REFRIGERATION 


99 


Stop  valves,  manifolds,  and  unions  connect  with  the  discharge  of 
the  compressor  and  the  liquid  ammonia  supply  to  the  receiver. 
In  the  manner  of  making  the  connections  to  this  type  of  con- 


denser and  the  taking  away  of  the  liquefied  ammonia  as  well  as  in 
the  devices  for  supplying  the  cooling  water,  a  great  variety  exists. 
Fig.  31  represents  a  side  elevation  of  an  ammonia  condenser  with 


100 


REFRIGERATION 


the  discharge  or  inlet  of  the  gas  from  the  compressor  entering  at  the 
top  A,  and  the  liquid  ammonia  taken  off  at  the  bottom  B,  while  the 
water  is  supplied  over  the  coils  flowing  down  into  the  catch-pan  or 
water-tight  floor,  where  it  accumulates  and  is  taken  away  by  any  of 


the  usual  means.  It  will  be  noticed  that  the  flow  of  the  water  and  the 
gas  with  this  type  of  condenser  is  in  the  same  direction,  the  coldest 
water  coming  in  contact  with  the  warmest  ammonia.  The  tempera- 
ture governing  or  determining  the  point  of  condensation  will  be  that 
at  which  the  ammonia  leaves  the  condenser,  or  the  temperature  in 


REFRIGERATION  101 

the  bottom  pipe  from  which  the  liquid  ammonia  is  withdrawn. 
Owing  to  this  arrangement  it  is  not  favorable  to  a  low  condensing 
pressure  or  economy  in  the  water  used.  Fig.  32  represents  a  type  in 
which  an  attempt  is  made  to  eliminate  this  undesirable  feature,  and 
in  which  it  is  expected  to  use  the  waste  from  the  condenser  proper, 
in  taking  out  the  greater  part  of  the  sensible  heat  from  the  gas  leaving 
the  compressor. 

The  construction  of  this  condenser  is  identical  with  that  shown 
in  the  preceding  figure  except  that  its  uppermost  pipe  is  continued 
down  and  under  the  pipes  forming  the  condenser  proper;  it  passes 
backward  and  forward  in  order  that  a  large  proportion  of  the  heat 
may  be  removed  by  the  water  from  the  condenser  proper,  before 
the  ammonia  enters  the  condenser.  A  supplemental  header  is 
sometimes  introduced  in  connection  with  this  pipe  for  removing 
any  condensation  taking  place  in  it. 

A  third  type  of  this  condenser  is  shown  in  Fig.  33.  In  this 
type  a  reverse  flow  of  the  gas  and  water  takes  place.  The  gas  en- 
ters the  condenser  through  a  manifold  or  header  A  at  the  bottom 
and  continues  its  flow  upward  through  the  pipes  to  the  top;  at  several 
points  drain  pipes  are  provided  for  taking  off  the  condensation 
into  the  header  B.  The  condensing  water  flows  downward  over 
the  pipes.  This  type  of  condenser  is  the  most  nearly  perfect  of  its 
class. 

The  atmospheric  condenser  is  a  favorite,  and  possesses  many 
features  that  make  it  preferable  to  the  submerged.  Its  weight  is  a 
minimum,  being  only  that  of  pipe  and  supports  and  a  small  amount 
of  water.  The  sections  or  banks  may  be  placed  at  a  convenient  dis- 
tance apart  to  facilitate  cleaning  and  repairs.  The  atmospheric 
effect  in  evaporating  a  portion  of  the  condensing  water  during  its  flow 
over  the  condenser,  makes  use  of  the  latent  heat  of  the  water  in  ad- 
dition to  the  natural  rise  in  its  temperature. 

The  various  devices  for  distributing  the  water  over  the  condenser 
are  numerous.  Fig.  34  represents  the  simplest  and  most  easily  ob- 
tained— a  simple  trough  with  perforations  at  the  bottom  for  allowing 
the  water  to  drip  over  to  the  concenser. 

Fig.  35  is  a  modification  of  the-  one  shown  in  Fig.  34.  This  is 
intended  to  prevent  the  clogging  of  the  perforations,  by  allowing  the 
water  to  flow  into  the  space  at  one  side  of  the  partition,  and  then 


102 


REFRIGERATION 


through  a  series  of  perforations  into  the  second,  and  thence  through 
a  second  set  of  perforations  in  the  bottom  to  the  pipes  in  the  con- 
denser. 


Fig.  34.    Simple  V;Shaped  Water  Trough. 


Fig.  35.    Modification  of  the  V-Shaped  Trough. 

Fig.  36  is  a  type  of  trough,  or  water  distributor,  designed  to 
overcome  the  objections  to  a  perforated  form  of  trough,  and  the 
consequent  difficulties  due  to  the  clogging  or  filling  of  the  perfora- 


REFRIGERATION 


103 


tions.  As  will  be  readily  understood  from  the  illustration,  this  is  also 
made  of  galvanized  sheet  metal  with  one  side  enough  higher  than 
the  other  to  cause  the  water  to  overflow  through  the  V-shaped  notches 
or  openings  along  the  top  of  the  straight  or  vertical  side  of  the  trough, 
and  down  and  off  the  serrated  bottom  edge  to  the  pipes. 

The  object  of  the  serrated  edges,  as  will  be  apparent,  is  the  more 
even  distribution  of  the  water,  owing  to  the  fact  that  while  it  would 
be  practically  impossible  to  obtain  a  uniform  flow  of  water  over  a 


Fig.  36.    Serrated-Edge  V-Trough. 

straight  and  even  edge  of  a  trough,  particularly  if  the  amount  is  limited, 
it  is  an  easy  matter  to  regulate  the  flow  through  the  V-shaped  openings. 
Fig.  37  is  termed  the  slotted  water  pipe.  It  is  a  pipe  slotted 
between  its  two  ends,  from  which  the  water  overflows  to  the  series 
of  pipes  below.  It  is  good  practice  to  lead  the  water  supply  to  a 
cast-iron  box  at  the  center  of  the  condenser,  into  the  sides  of  which 
is  screwed  a  piece  of  pipe- — usually  2-inch — reaching  the  ends  of  the 
condenser,  and  having  its  outer  ends  capped,  which  may  be  removed 
while  a  scraper  is  passed  through  the  slot  from  the  center  towards 
the  ends  while  the  water  is  still  flowing,  thereby  carrying  off  any 
deposit  within  the  pipe.  This  forms  a  very  durable  construction, 
and  one  not  liable,  as  with  the  galvanized  drip  trough,  to  disarrange- 
ment or  bending  out  of  shape  due  to  various  causes.  It  is  impossi- 


104 


REFRIGERATION 


ble,  however,  to  obtain  the  uniform  flow  of  water  over  the  condenser 
with  this,  as  with  the  serrated  or  perforated  troughs,  particularly  if 
the  supply  is  limited,  from  the  fact  as  stated  in  describing  the  over- 
flow trough,  viz,  the  impossibility  of  obtaining  a  sufficiently  thin 
stream  of  that  length. 

Double=Pipe  Condenser.  This  is  a  modern  adaptation  of  an  old 
idea,  given  up  owing  to  its  complex  construction  and  the  imperfect 
facilities  available  for  its  manufacture.  It  has  come  into  use  with 
great  rapidity,  and  has  brought  forth  many  novel  ideas  of  principle 
and  construction.  It  combines  the  good  features  of  both  the  atmos- 


Flg.  37.    Slotted  Water  Pipe. 

pheric  and  the  submerged  types,  having  small  weight  and  being 
accessible  for  repairs.  It  has  the  downward  flow  of  the  ammonia 
and  the  upward  flow  of  the  water,  effecting  a  complete  counter  flow  of 
the  two,  minimizing  the  amount  of  water  required  and  taking  up 
the  heat  of  condensation  with  the  least  possible  difference  between 
the  ammonia  and  the  water. 

The  two  general  forms  of  construction  are  a  combination  of  a 
1^-inch  pipe  within  a  2-inch  pipe,  or  a  2-inch  pipe  within  a  3-inch. 
The  water  passes  upward  through  the  inner  pipe,  while  the  gas  is 
discharged  downward  through  the  annular  space;  or,  the  position 
of  the  two  may  be  reversed,  the  ammonia  being  within  the  inside 
pipe  while  the  water  travels  upward  through  the  annular  space. 


REFRIGERATION 


105 


106 


REFRIGERATION 


REFRIGEEATION 


107 


108 


REFRIGERATION 


They  are  also  constructed  in  series,  in  which  the  gas  enters  a  number 
of  pipes  of  a  section  at  one  time,  flowing  through  these  to  the  opposite 
end  to  a  header  or  manifold,  at  which  point  the  number  of  pipes  is 
reduced,  and  so  on  to  the  bottom  with  a  constantly  reduced  area. 
The  theory  of  this  construction  is,  that  the  volume  of  the  gas  is 


Fig.  41. 


Fig.  42. 
Types  of  Oil  Interceptors 


Fig.  43. 


constantly  reduced  as  it  is  being  condensed.     Figs.  38,  39,  and  40 
illustrate  a  general  range  of  the  various  types  in  use. 

It  is  usual  in  the  construction  of  this  type  to  make  each  section 
or  bank  twelve  pipes  high  by  about  17£  feet  long;  they  are  rated 
nominally  at  ten  tons  refrigerating  capacity  each,  although  for  uneven 
units  the  construction  is  made  to  vary  from  10  to  14  pipes  in  each. 


REFRIGERATION  109 

Oil  Separator  or  Interceptor.  This  is  a  device  or  form  of 
trap,  placed  on  the  line  of  the  discharge  between  the  compressor  and 
the  condenser  to  separate  the  oil  from  the  ammonia  gas.  It  is  to 
prevent  the  pipe  surface  of  the  condensing  and  evaporating  system 
from  becoming  covered  with  oil,  which  acts  as  an  insulator  and 
prevents  rapid  transmission  of  heat  through  the  walls. 

There  are  many  forms  of  this  device  in  common  use,  including 
the  plain  cylindrical  shell  with  an  inlet  at  one  side  or  end  and 
an  outlet  at  the  other,  an  almost  endless  variety  of  baffle  plates, 
spiral  conductors,  and  reverse-current  devices.  The  object  is  similar 
to  that  obtained  in  the  steam  or  exhaust  separator,  and  generally 
speaking,  that  which  would  be  effective  in  one  sendee  would  be  so 
in  the  other.  Figs.  41,  42,  and  43  illustrate  three  of  the  most  com- 
mon types  in  use;  from  these  the  student  will  understand  the 
general  principles. 

COOLING  TOWERS 

In  cities  and  other  localities  where  water  is  scarce  or  of  high 
temperature,  it  becomes  important  to  conserve  the  supply  brought 
to  the  plant.  In  order  to  do  this  it  is  necessary  to  cool  the  water 
after  it  has  passed  over  the  condensers  and  coolers  of  the  refrigera- 
ting plant.  This  is  done  by  evaporation  of  a  part  of  the  water  under 
atmospheric  pressure  so  that  the  remaining  water  will  be  cooled, 
owing  to  the  abstraction  of  heat  that  becomes  latent  in  the  water 
evaporated.  The  process  may  be  employed  to  advantage,  even 
where  there  is  plenty  of  water,  in  order  to  save  pumping;  or  where 
the  water  is  taken  from  muddy  streams  to  a  settling  basin,  to  avoid 
the  use  of  more  muddy  water  than  absolutely  required.  The  effi- 
ciency of  any  apparatus  for  this  purpose  depends  on  the  extent  of  the 
water  surfaces  exposed  and  on  the  amount  of  air  brought  in  contact 
with  the  water.  Also  to  some  extent  the  pressure  of  the  air  and,  to 
greater  extent,  the  dryness  of  the  air  are  factors  having  their  influence, 
but  acting  alike  on  any  apparatus  however  constructed. 

Apparatus  designed  to  cool  water  for  re-use  in  refrigerating 
plants  are  known  as  cooling  towers  and  of  these  there  are  many 
types  on  the  market.  All  such  towers  may  be  divided  into  two  classes 
according  to  whether  the  circulation  of  air  is  by  natural  or  artificial 
currents.  Also  towers  are  classified  as  to  material  used,  whether 


110 


KEFRIGERATION 


steel  or  wood.     Both  materials  are  used  for  towers  operating  with 
both  kinds  of  air  circulation.    An  efficient  tower  can,  in  fact,  be  made 


Fig.  44.    Atmospheric  Wood  Cooling  Tower. 


very  cheaply  by  throwing  brush  into  a  framework  arranged  to  pre- 
vent the  brush  packing,  thus  leaving  space  for  air  currents.     Where 


REFRIGERATION 


111 


wood  is  used,  the  tower  may  be  anything  from  a  cheap  slatted  struc- 
ture made  of  rough  lumber  to  an  elaborate  tower  such  as  shown  in 


Fig.  44.     Here  No.  1  lumber  is  used  and  treated  by  a  preservative 
process  before  being  put  into  the  tower,  and  the  structure  is  painted 


112 


REFRIGERATION 


with  mineral  paint  when  finished.  This  illustration  represents  the 
tower  constructed  for  the  Bauer  Ice  Cream  and  Baking  Co.  of  Cin- 
cinnati, O.,  by  the  Triumph  Ice  Machine  Co.,  for  a  75-ton  refrigera- 
ting plant  using  city  water.  Fig.  45  shows  a  circular  steel  tower 
using  forced  air  circulation  installed  by  the  Triumph  people  for  the 
Cincinnati  Ice  Co. 

A  good  form  of  the  atmospheric  or  natural  draft  steel  tower 
is  made  by  B.  Franklin  Hart  Jr.  and  Co.  of  New  York,  as  shown 
by  Fig.  46,  complete  with  spray  preventors.  In  towers  using  natural 


Fig.  46.    Cooling  Tower  Installed  at  a  Large  Brewery  in  Monterey,  Mexico. 

air  currents,  care  should  be  taken  to  set  the  apparatus  clear  of  all 
buildings,  etc.,  so  that  there  is  free  access  of  the  air.  Such  towers 
should  be  designed  with  about  12  square  feet  of  cooling  surface  for 
each  5  gallons  of  water  to  be  cooled  per  minute,  with  which  surface 
the  temperature  of  the  water  will  be  lowered  from  7  to  15  degrees 
depending  on  conditions.  From  1^  to  7  per  cent  of  the  water  passed 
over  the  tower  is  evaporated,  and  with  losses  by  leakage,  etc.,  this 
may  be  increased  to  10  or  12  per  cent,  which  represents  the  amount 
of  make-up  water  that  must  be  supplied.  With  artificial  draft 
from  5  to  25  horse-power  is  required  to  operate  the  fans,  according 
to  the  size  of  the  tower  and  the  type  of  fan  used.  Either  suction  or 
pressure  fans  may  be  used  in  such  towers,  as  it  is  not  definitely  settled 
whether  best  results  are  had  by  forcing  air  in  at  the  bottom  of  the 
tower  or  drawing  it  down  from  the  top.  Most  towers,  however, 


REFRIGERATION 


113 


force  the  air  in  at  the  bottom,  thereby  getting  the  flow  in  the  opposite 
direction  to  that  of  the  water. 

EVAPORATORS 

Evaporators  may  be  divided  into  two  classes.  The  first  is 
operated  in  connection  with  the  brine  system.  In  this  evaporator 
salt  brine,  or  other  solution,  is  reduced  in  temperature  by  the  evapo- 
ration of  the  ammonia  or  other  refrigerant,  and  the  cooled  brine 
circulated  through  the  room  or  other  points  to  be  refrigerated.  In 
the  second,  the  direct-expansion  system,  the  ammonia  or  refrigerant 
is  taken  directly  to  the  point  to  be  cooled,  and  there  evaporated  in 


.         Fig.  47.    Rectangular  Brine-Cooling  Tank. 

pipes  or  other  receptacles,  in  direct  contact  with  the  object  to  be 
cooled.  Which  of  the  two  systems  is  the  better,  is  a  much  disputed 
and  debated  point;  we  can  state,  in  a  general  way,  that  both  have 
their  advantages,  and  each  is  adapted  to  certain  classes  of  duty. 

The  cooling  of  brine  in  a  tank  by  a  series  of  evaporating  coils 
—one  of  the  earliest  methods — is  common  to-day.  A  description 
of  the  many  methods  of  construction  and  equipment  would  require 
much  space.  Let  us,  therefore,  discuss  the  two  most  general  types, 
viz,  the  rectangular  with  flat  coils,  and  the  double-pipe  cooler — the 
spiral-coil  cooler  being  practically  obsolete. 


1 1 4  REFRIGERATION 

Brine  Tank.  Fig.  47  shows  a  sectional  view  of  a  brine-cooling 
tank.  Flat  or  zigzag  evaporating  coils  are  connected  to  manifolds 
or  headers;  the  pipe  connections  leading  to  and  from  these  manifolds 
for  the  proper  supplying  of  the  liquid  ammonia  and  the  taking  away 
or  return  of  the  gas  to  the  compressor  are  also  shown.  For  coils  of 
this  type,  1-inch  or  IJ-inch  pipe  is  preferable,  owing  to  the  impos- 
sibility of  bending  larger  sizes  to  a  small  enough  radius  to  get  the 
required  amount  into  a  tank  of  reasonable  dimensions.  It  is  pos- 
sible to  make  coils  of  this  construction  of  any  desired  length  or  num- 
ber of  pipes  to  the  coil,  "pipes  high,"  the  bends  being  from  3^  in. 
to  4  in.  centers  for  1-inch  pipe,  and  4  in.  to  5  in.  for  lj-inch 
pipe.  It  is  preferable  to  make  the  coils  of  moderate  length — 
not  less  than  150  feet  in  each — and  there  is  no  disadvantage,  other 
than  in  handling,  in  making  them  to  contain  up  to  500  or  600  feet 
each.  It  will  be  observed  that  there  is  a  slight  downward  pitch  to 
the  pipes  with  a  purge  valve  at  the  lowest  point  of  the  bottom  mani- 
fold, which  is  valuable  and  an  almost  necessary  provision.  This 
valve  is  for  removing  foreign  matter  that  may  enter  the  pipes  at  any 
time.  By  opening  the  valve  and  drawing  a  portion  of  their  contents, 
the  condition  of  cleanliness  can  be  determined  without  the  necessity 
of  shutting  down  and  removing  the  brine  and  ammonia  for  inspec- 
tion. The  coils  are  usually  strapped  or  bound  with  flat  bar  iron 
about  |  inch  X  2  inches,  or  a  little  heavier  for  the  longer  coils,  and 
bolted  together  with  J-inch  square-head  machine  bolts.  The  coils 
are  painted  with  some  good  water-proof  or  iron  paint. 

The  brine  tank  is  usually  constructed  of  iron  or  steel  plates, 
varying  from  T\  inch  to  f  inch  in  thickness;  the  average  being  ^ 
inch  for  tanks  of  ordinary  size.  The  workmanship  and  material 
for  a  tank  of  this  kind  should  be  of  the  very  best;  without  these 
the  result  is  almost  certain  to  be  disastrous  to  the  owner  or  builder. 
The  general  opinion  with  iron  workers,  before  they  have  had  ex- 
perience, is  that  it  is  a  simple  matter  to  make  a  tank  which  will  hold 
water  or  brine,  and  that  any  kind  of  seam  or  workmanship  will  be 
good  enough  for  the  purpose.  On  the  contrary  the  greatest  care 
and  attention  to  detail  is  necessary.  It  is  customary,  and  good  prac- 
tice, to  form  the  two  side  edges  at  the  bottom  by  bending  the  sheets, 
thereby  avoiding  seams  on  two  sides;  while  for  the  ends  an  angle 
iron  may  be  bent  to  conform  to  this  shape  and  the  two  sheets  then 


REFRIGERATION  115 

riveted  to  the  flanges  of  the  angle  iron.  The  edges  of  the  sheets 
should  be  sheared  or  planed  bevel,  and  after  riveting,  calked  inside 
and  out  with  a  round-nosed  calking  tool.  The  rivets  should  be  of 
full  size,  as  specified  for  boiler  construction,  and  of  length  sufficient 
to  form  a  full  conical  head  of  height  equal  to  the  diameter  of  the 
rivet,  and  brought  well  down  onto  the  sheet  at  its  edges.  An  angle 
iron  of  about  3  inches  should  be  placed  around  the  top  edge  and 
riveted  to  the  side  at  about  12-inch  centers. 

One  or  more  braces,  depending  on  the  depth,  should  extend 
around  the  tank  between  the  top  and  bottom,  to  prevent  bulging; 
without  these  it  would  be  impossible  to  make  the  tank  remain  tight, 
as  a  constant  strain  is  on  all  its  seams.  A  very  good  brace  for  the 
purpose  is  a  deck  beam.  Flat  bar  iron  placed  edge-wise  against 
the  tank  writh  an  angle  iron  on  each  side  and  all  riveted  through 
and  to  the  side  of  the  tank  with  splice  plates  at  the  corners,  or  one 
of  each  pair  long  enough  to  lap  over  the  other,  makes  a  good  brace. 
Heavy  T-iron  is  also  used  to  some  extent.  It  is  usual  to  rivet  the 
bottom  of  the  tank  and  a  short  distance  up  the  sides,  then  test  by 
filling  with  water;  if  tight,  lower  the  tank  to  its  foundation  and  com- 
plete the  riveting  and  calking.  It  may  then  be  filled  with  water  and 
tested  until  proven  absolutely  tight,  when  it  may  be  painted  with 
some  good  iron  paint;  it  is  now  ready  for  its  equipment  of  coils  and 
insulation. 

A  washout  opening  with  stop  valve  should  be  placed  in  the 
bottom  at  one  corner;  for  this  purpose  it  is  well  to  have  a  wrought 
iron  flange,  tapped  for  the  size  of  pipe  required,  riveted  to  the 
outside  of  the  bottom.  If  the  brine  pump  can  be  located  at  this 
time,  it  is  well  to  have  a  similar  flange  for  the  suction  pipe  riveted 
to  the  side  or  bottom  of  the  tank,  as  a  bolted  flange  with  a  gasket 
is  never  as  durable  as  a  flange  put  on  in  this  manner. 

After  the  tank  has  been  made  absolutely  tight  and  painted, 
the  insulation  may  be  put  around  it,  the  insulated  base  or  founda- 
tion having  been  put  in  previous  to  the  arrival  of  the  tank.  The 
insulation  should  be  constructed  of  joists  2  in.  or  3  in.  X  12  in.,  on 
edge,  and  the  space  should  be  filled  in  with  any  good  insulating  ma- 
terial and  floored  over  with  two  thicknesses  of  tongued  and  grooved 
flooring  with  paper  between  the  thicknesses.  In  putting  the  insula- 
tion on  the  sides  and  ends  of  the  tank,  place  joists,  2  in.  X  4  in., 


116  REFRIGERATION 

so  that  they  rest  on  the  projecting  edges  of  the  foundation  about 
2  feet  apart.  The  upper  ends  should  be  secured  to  the  angle 
iron  at  the  top  of  the  tank,  its  upper  flange  having  been  punched 
with  f-inch  holes,  18  in.  to  24  in.  centers,  and  to  which  it  is  well 
to  bolt  a  plank,  having  its  edge  project  the  required  distance  to 
receive  the  uprights.  Between  the  braces  around  the  tank,  block- 
ings should  be  fitted  to  secure  the  framework  at  the  middle,  as  the 
height  of  some  tanks  is  too  great  to  depend  on  the  support  at  the 
top  and  the  bottom  alone. 

After  the  framework  has  been  properly  formed  and  secured 
to  the  base  and  tank,  take  1-inch  flooring,  rough,  or  planed  on  one 
side,  and  board  up  on  the  outside  of  the  uprights.  Fill  in  the 
space,  as  the  work  progresses,  with  the  insulating  material  which  may 
be  any  one  of  the  usual  materials.  Granulated  cork  is  about  the 
best,  all  things  considered,  although  charcoal,  dry  shavings,  saw- 
dust, or  other  non-conductors  may  be  used  with  good  results.  When 
the  first  course  of  boards  is  in  place,  it  is  well  to  tack  one  or  two 
thicknesses  of  good  insulating  paper  against  the  outer  surface,  care 
being  taken  that  the  joints  lap  well  and  that  bottoms  and  corners 
are  filled  and  turned  under  at  the  junction  with  the  bottom  insula- 
tion. It  is  then  in  shape  for  the  final  or  outer  course  which  is  very 
often  made  of  some  of  the  hard  woods  in  2^-inch  or  3-inch  widths, 
tongued,  grooved,  and  beaded.  It  is  finished  off  with  a  base  board 
at  the  bottom,  moulding  at  the  top,  and  given  a  hard  wood  finish 
in  oil  or  varnish.  If  the  tank  is  located  in  a  part  of  the  building  in 
which  appearance  is  of  no  importance,  the  outer  course  may  be  a 
repetition  of  the  first,  except  that  the  boards  are  put  on  vertically 
instead  of  horizontally. 

It  is  well  to  make  the  top  of  the  tank  in  removable  sections 
to  facilitate  examination  or  cleaning;  for  this  purpose  make  a  num- 
ber of  sections,  about  2  J  to  3  feet  wide,  of  the  length  or  width  of  the 
tank,  using  joists  about  2  in.  X  6  in.  placed  on  edge,  floored 
over  top  and  bottom,  and  filled  in  with  the  selected  insulating  ma- 
terial. It  is  also  well  to  have  a  small  lid  at  one  end  of  each,  prefer- 
ably over  the  headers  or  manifolds,  which  will  allow  of  internal 
examination  of  the  tank  to  ascertain  the  height  or  strength  of  brine 
without  removing  the  larger  sections.  The  tank  is  now  fully  equipped 
and  ready  for  testing  and  filling  with  brine. 


REFRIGERATION 


117 


For  a  circular  tank,  the  general  instructions  regarding  construc- 
tion and  insulation  may  apply  as  with  the  rectangular  tank  just 
described;  therefore  only  its  special  features  will  be  considered. 
If  the  tank  is  small  and  there  is  sufficient  head  room  above  it  for 
handling  the  coils  there  cannot  be  serious  objection  to  this  type,  as 
its  cost  is  lower  than  that  of  the  rectangular  tank.  This  is  often  an 


Fig.  48.    Circular  Brine-Cooling  Tank. 

important  item  in  a  small  installation,  but  when  the  tank  is  of  con- 
siderable size  and  the  coils  large  it  is  not  as  readily  handled  and 
taken  care  of  as  the  other  type.  The  usual  construction  of  a  nest  of 
coils  for  a  round  tank  is  to  bend  the  inside  coil  to  as  small  a  circle  as 
possible,  which,  if  it  be  of  1-inch  or  1  J-inch  pipe,  may  be  6  to  8  inches. 
Increase  each  successive  coil  enough  to  pass  over  the  next  smaller 
until  the  required  amount  of  pipe  is  obtained.  The  ends  may  then 
be  bent  up  or  out  and  joined  to  headers  at  the  top  and  the  bottom 


118 


REFRIGERATION 


and  the  tank  insulated  in  the  manner  previously  described;  it  is 
then  ready  to  test  and  charge  with  ammonia  and  brine.  Fig.  48 
represents  an  evaporator  of  this  type. 

Other  constructions  of  tanks  and  coils  are  too  numerous  to  de- 
scribe in  detail,  and  with  one  exception  may  be  properly  classed 
in  one  of  the  preceding  types.  The  one  exception  referred  to  is 
illustrated  in  Fig.  49.  It  is  quite  common  and  is  adopted  for  large 
pipe;  it  is  often  called  oval,  although  not  of  that  shape,  but  rather 
a  combination  of  the  flat  and  circular  form.  It  has  some  good 


Pig.  49.    Oval  Brine-Cooling  Tank. 

features;  it  allows  the  maximum  amount  of  pipe  in  the  smallest  space 
and  a  large  amount  of  pipe  in  a  single  coil. 

Brine  Cooler.  The  brine  cooler  at  present  is  a  popular  and 
efficient  method  of  cooling  brine  for  general  purposes.  Owing  to 
mechanical  defects  and  the  impossibility  of  obtaining  a  brine  solu- 
tion which  would  not  freeze,  it  was  abandoned  only  to  be  taken  up 
again,  and  with  the  aid  of  modern  ideas  and  better  material  it  has 
become  highly  successful.  The  great  advantage  of  the  brine  cooler 
over  the  tank  method  of  cooling  brine  is  the  fact  that  the  brine  and 
gas  are  both  in  circulation,  passing  through  the  double-pipe  cooler 
in  opposite  directions  so  as  to  get  the  greatest  efficiency  as  well  as 


REFRIGERATION 


119 


120 


REFRIGERATION 


the  most  rapid  transfer  of  heat  and  resulting  rapid  cooling.  The 
double-pipe  cooler  is  almost  universally  used  at  the  present  time  in 
preference  to  the  spiral  enclosed  shell  cooler,  notwithstanding  the 
fact  that  the  latter  is  more  easily  insulated  and  has  a  larger  space 
for  evaporation  of  the  gas.  Double-pipe  coolers  must  be  set  up  in 

TABLE  XVII 

Properties  of  Calcium  Brine  Solution 


DEG.X 
BAUME 
60°  F. 

DEO. 
SALOM- 

ETER 

60"  F. 

PER  CENT 
CALCIUM 

WEIGHT 

LBS.  PER 
Cu.  FT. 
SOL. 

LBS. 

PER 

GAL- 
LON 

SPECIFIC 
GRAVITY 

SPECIFIC 
HEAT 

FREEZING 
POINT  F. 

AMMONI.. 
GAUGE 
PRESSURE 

0 

0 

0 

0 

0 

1 

1 

32 

47.31 

1 

4 

.943 

1.25 

i 

1.007 

.996 

31.1 

46.14 

2 

8 

1  .886 

2.5 

} 

1.014 

.988 

30.33 

45  .  14 

3 

12 

2.829 

3.75 

4 

1.021 

.98 

29.48 

44.06 

4 

16 

3.772 

5 

I    ^ 

1.028 

.972 

28.58 

43 

5 

20 

4.715 

6.25 

% 

1.036 

.964 

27.82 

42.08 

6 

24 

5.658 

7.5 

1 

1.043 

.955 

27.05 

41.17 

7 

28 

6.601 

8.75 

if 

1.051 

.946 

26.28 

40.25 

8 

32 

7.544 

10 

H 

1.058 

.936 

25.52 

39.35 

9 

36 

8.487 

11.25 

H 

1.066 

.925 

24.26 

37.9 

10 

40 

9.43 

12.5 

1$  ' 

1.074 

.911 

22.8 

36.3 

11 

44 

10.373 

13.75 

it 

1.082 

.896 

21.3 

34.67 

12 

48 

11.316 

15 

2 

1.09 

.89 

19.7 

32.93 

13 

52 

12.259 

16.25 

2i 

1.098 

.884 

18.1 

31.33 

14 

56 

13.202 

17.5 

2i 

1.107 

.878 

16.61 

29.63 

15 

60 

14.145 

18.75 

2J 

1.115 

.872 

15.14 

28.35 

16 

64 

15.088 

20 

2§ 

1.124 

.866 

13.67 

27.04 

17 

68 

16.031 

21.25 

2f 

1  .  133 

.86 

12.2 

25.76 

18 

72 

16.974 

22.5 

3 

1.142 

.854 

10 

23.85 

19 

76 

17.917 

23.75 

3* 

1.151 

.849 

7.5 

21.8 

20 

80 

18.86 

25 

3i 

1.16 

.844 

4.6 

19.43 

21 

84 

19.803 

26.25 

3i 

1.169 

.839 

1.7 

17.06 

22 

88 

20  .  746 

27.5 

3J 

1.179 

.834 

-  1.4 

14.7 

23 

92 

21.689 

28.75 

3f 

1.188 

.825 

—  4.9 

12.2 

24 

96 

22.632 

30 

4 

1.198 

.817 

—  8.6 

9.96 

25 

100 

23.575 

31.25 

4£ 

1.208 

.808 

—11.6 

8.19 

26 

24.518 

32.5 

4i 

1.218 

.799 

—17.1 

5.22 

27 

25.461 

33.75 

4i 

1.229 

.79 

—21.8 

2.94 

28 

26.404 

35 

4§ 

1.239 

.778 

—27. 

65 

29 

27.347 

36.25 

*! 

1.25 

.769 

—32.6 

1"  Vac. 

30 

28.29 

37.5 

5         ' 

1   261 

.757 

—39.2 

8.5"" 

31 

29.233 

38.75 

si 

1.272 

—46.3 

12 

32 

30.176 

40 

6J 

1.283 

—54.4 

15 

33 

31.119 

41.25 

«* 

1.295 

—52.5 

10 

34 

32.062 

42.5 

5f 

1.306 

—39.2 

4 

35 

33 

43.75 

6| 

1.318 

—25.2 

1.5 

REFRIGERATION 


121 


insulated  rooms  at  considerable  expense,  but  the  comparative  sim- 
plicity of  the  construction  and  the  fact  that  all  parts  are  open  and 
subject  to  inspection,  has  made  this  form  of  cooler  the  choice  of  prac- 
tically all  refrigerating  engineers  in  recent  years. 

Owing  to  the  fact  that  salt  brine  may  freeze  and  burst  the  pipes 
of  the  cooler,  it  should  not  be  used  if  avoidable.  Calcium  chloride 
brine  is  preferred  for  several  reasons,  but  particularly  on  account 
of  the  fact  that  its  freezing  point  for  ordinary  densities  is  54°  below 
zero  F.;  while  that  of  salt  brine  is  about  0°  F.  The  construction  of 

TABLE  XVIII 
Properties  of  Salt  Brine  Solution 


DEGREES 

ON 

SALOM. 

r^ir—  R 

WEIGHT       Cu'   FT' 

POUNDS 
SALT  PER 
GALLON 

SPECIFIC 
GRAVITY 

SPECIFIC 
HEAT 

FREEZING 
POINT  F. 

AMMONIA 
GAUGE 
PRESSURE 

0 

0 

0 

0 

1 

1 

32 

47.32 

5 

1.25 

.785 

.015 

1.009 

.99 

30.3 

45.1 

10 

2.5 

1.586 

.212 

1.0181 

.98 

28.6 

43  .03 

15 

3.75 

2.401 

.321 

1.0271 

.97 

26.9 

41 

20 

5 

3.239 

.433 

1  .0362 

.96 

25.2 

38.96 

25 

6.25 

4.099 

'.548 

1.0455 

.943 

23.6 

37.19 

30 

7.5 

4.967 

.664 

1  .0547 

.926 

22 

35.44 

35 

8.75 

5.834 

.78 

1.064 

.909 

20.4 

33.69 

40 

10 

6.709 

.897 

1.0733 

.892 

18.7 

31.93 

45 

11.25 

7.622 

1.019 

1  .0828 

.883 

17.1 

30.33 

50 

12.5 

8.542 

1.142 

1  .0923 

.874 

15.5 

28  73 

55 

13.75 

9.462 

1.265 

1.1018 

.864 

13.9 

27.24 

60 

15 

10  .  389 

1.389 

1.1114 

.855 

12.2 

25.76 

65 

16.25 

11.384 

1.522 

1.1213 

.848 

10.7 

24.46 

70 

17.5 

12.387 

1.656 

1.1312 

.842 

9.2 

23.16 

75 

18.75 

13.396 

1.791 

1.1411 

.835 

7-7 

21.82 

80 

20 

14.421 

1.928 

1.1511 

.829 

6.1 

20.43 

85 

21.25 

15.461 

2.067 

1.1614 

.818 

4.6 

19.16 

•     90 

22.5 

16.508 

2.207 

1.1717 

.806 

3.1 

18.2 

95 

23  .  75 

17.555 

2.347 

1.182 

.795 

1.6 

16.88 

100 

25 

18.61 

2.488 

1.1923 

.783 

0 

15.67 

the  double-pipe  brine  cooler  is  shown  in  Fig.  50,  in  which  it  is  seen 
that  one  pipe  is  within  the  other,  the  brine  being  discharged  by  the 
pumps  into  one  or  more  pipes  as  at  A  and  issuing  at  B.  This  con- 
nection leads  from  the  main  to  the  point  to  be  refrigerated,  and  the 
ammonia  is  expanded  or  fed  into  the  annular  space  between  the 
two  pipes  and  takes  up  the  heat  of  the  brine  in  evaporating,  issuing 
as  gas  from  the  opening  D  at  the  top  of  the  cooler.  From  thence  the 
ammonia  flows  to  the  compressor  and  passes  through  the  cycle  of 
compression,  condension,  and  return  to  the  liquid  ammonia  receiver  as 


122  REFRIGERATION 

before.  The  ammonia  evaporating  between  the  two  pipes  will 
naturally  absorb  as  much  heat  from  the  outside  surface  as  from  the 
inner  or  brine,  if  allowed  to  do  so,  and  it  therefore  becomes  necessary 
to  insulate  the  outside  of  the  cooler  or  to  build  an  insulated  room 
in  which  the  cooler  is  erected. 

Although  preferable  in  all  cases,  calcium  brine  is  a  necessity 
for  very  low  temperatures.  The  proper  density  or  strength  of  either 
salt  or  calcium  brine  is  determined  by  the  temperature  to  which  it 
is  necessary  that  the  brine  be  reduced.  In  determining  the  proper 
strength  for  different  requirements,  Tables  17  and  18  are  of  value. 
It  should  be  remembered,  however,  that  a  difference  of  from  5  to  10 
degrees  F.  exists  between  the  temperature  of  the  brine  and  that  of 
the  evaporating  ammonia;  and  that  while  the  strength  of  the  brine 
may  appear  ample  for  the  temperature  carried,  the  lower  temperature 
of  the  liquid  ammonia  may  cause  it  to  solidify  within  or  upon  the 
surface  of  the  evaporator,  thus  causing  it  to  separate,  or  freeze,  and 
act  as  an  insulator,  preventing  the  transmission  of  heat  through  the 
surface.  It  is,  therefore,  necessary  in  examining  into  the  strength 
of  the  brine  to  consider  it  with  reference  to  the  evaporating  pres- 
sure of  the  ammonia  as  well  as  its  own  temperature.  In  the 
last  columns  of  Tables  17  and  18,  the  gauge  pressures,  correspond- 
ing to  the  freezing  point  of  the  brine  for  different  strengths,  are 
given. 

The  usual  and  proper  instrument  for  determining  the  strength 
of  brine  is  the  Baumd  scale  already  described  in  discussing  aqua 
ammonia  and  its  strength,  but  an  instrument  known  as  the  salometer 
is  sometimes  used.  This  instrument  is  similar  in  appearance  to  the 
Baume"  hydrometer,  the  difference  being  the  way  in  which  the  scale 
is  graduated,  which  in  case  of  the  salometer  is  from  0  to  100,  the 
lower  point  being  that  at  which  the  tube  stands  when  floating  in 
pure  water,  while  the  100  point  is  that  at  which  it  stands  in  a 
saturated  solution  of  salt  brine,  i.  e.,  a  solution  which  can  be  made 
no  stronger,  owing  to  the  fact  that  the  water  has  dissolved  all  the 
salt  it  will  take  up.  In  the  table  giving  the  properties  of  calcium 
brine,  the  two  scales  are  compared  so  that  the  student  should  have 
no  trouble  in  converting  readings  of  one  scale  to  the  corresponding 
readings  of  the  other.  It  will  be  seen  that  the  scales  are  to  each 
other  as  1  to  4.  In  testing  the  strength  of  brine  a  sample  is  drawn 


REFRIGERATION  123 

into  a  test  tube  and  the  temperature  adjusted  to  60  degrees,  when 
the  reading  of  the  scale  is  taken  at  the  surface  of  the  liquid. 

In  making  brine  it  is  well  to  fit  up  a  box  with  a  perforated  false 
bottom,  or,  a  more  readily  obtained  and  equally  effective  mixer 
may  be  made  by  taking  a  tight  barrel  or  hogshead,  into  which  is 
fitted  a  false  bottom  four  to  six  inches  above  the  bottom  head,  and 
which  is  bored  with  one-half  inch  holes.  Over  the  false  bottom  lay 
a  piece  of  coarse  canvas  or  sack  to  prevent  the  salt  falling  through. 
A  water  connection  is  made  in  the  side  of  the  barrel  near  the  bottom, 
between  the  bottom  head  and  the  false  bottom,  and  a  controlling 
valve  placed  nearby  to  regulate  the  amount  of  water  passing  through. 


Fig.  51.    Apparatus  for  Preparing  Brine. 

An  overflow  connection  is  made  near  the  top  of  the  cask,  with  its 
end  so  placed  that  the  brine  will  flow  into  the  tank,  and  a  wire  screen 
placed  across  its  end  inside  the  cask  with  a  liberal  space  between  it 
and  the  opening,  to  allow  of  cleaning,  as  shown  in  Fig.  51.  The 
cask  or  barrel  is  now  filled  with  the  calcium  or  salt,  which  dissolves 
and  overflows  into  the  brine  tank. 

A  test  tube  and  Baume  scale,  or  salometer,  should  be  kept  at 
hand,  and  frequent  tests  made;  the  strength  of  the  brine  may  be 
regulated  by  admitting  the  water  more  or  less  rapidly.  After  the 
first  charge  it  is  well  to  allow  the  mixer  to  remain  in  position  for 
future  requirements.  A  connection  should  be  made  between  the 
return  brine  line  from  the  refrigerating  system  and  the  cask  with 


124  REFRIGERATION 

a  controlling  valve;  by  the  use  of  this  valve  the  strength  or  density 
of  the  brine  may  be  increased  without  adding  to  the  quantity.  The 
cask  should  be  kept  full  of  the  calcium  or  salt,  and  a  portion  of 
the  return  flow  of  brine  should  be  allowed  to  pass  through  the 
cask,  which  will  dissolve  the  contents  and  flow  into  the  tank. 

Calcium  is  usually  obtained  in  sheet-iron  drums,  holding  about 
600  pounds  each,  and  is  in  the  shape  of  a  solid  cake  within  the 
drum.  It  is  advisable  to  roll  these  onto  the  floor  or  top  of  the  tank' 
in  which  the  brine  is  to  be  made  and  pound  them  with  a  sledge  ham- 
mer before  removing  the  iron  casing,  this  process  breaking  it  up  into 
small  pieces  without  its  flying  about  the  room.  After  breaking  it  up 
the  shell  may  be  taken  off  and  the  contents  shoveled  into  the  mixer. 

It  is  also  sold  and  shipped  in  liquid  form,  in  tank  cars,  generally 
in  a  concentrated  form,  on  account  of  freight  charges,  and  diluted 
to  the  proper  point  upon  being  put  into  the  plant.  Where  proper 
railroad  facilities  exist,  this  is  probably  the  most  desirable  way  of 
obtaining  the  calcium. 

Salt  is  sold  and  may  be  obtained  in  a  number  of  forms.  The 
usual  shape  for  brine  is  the  bulk,  or  in  sacks  of  about  200  pounds 
each.  Where  it  is  possible  to  handle  salt  in  bulk,  direct  from  the 
car  to  the  tank,  this  is  most  generally  used  on  account  of  the  price, 
being  about  $1.00  per  ton  less  than  if  sacked.  If  it  is  necessary 
for  it  to  be  carted  or  stored  before  using,  the  sack  form  is  preferable. 
The  coarser  grades  of  salt  are  used  for  this  purpose,  No.  2  Mine 
being  the  grade  commonly  used.  The  finer  salts  are  higher  in  price, 
without  a  corresponding  increase  in  strength  of  the  brine  formed. 

As  a  rule  the  freezing  point  of  brine  should  be  equal  to,  or  slightly 
below,  the  temperature  of  the  evaporating  ammonia,  rather  than  the 
temperature  of  the  coldest  brine,  as  is  common.  In  referring  to  the 
table  of  salt  brine  solution,  page  121,  we  find  that  if  we  wish  to 
carry  a  temperature  of  10°  F.  in  the  outgoing  brine,  it  is  necessary 
that  the  temperature  of  the  evaporating  ammonia  be  from  5  degrees 
to  10  degrees  below  this  point,  in  order  that  the  transfer  of  heat  from 
the  brine  to  the  ammonia  will  be  rapid  enough  to  be  effective,  which 
would  mean  that  the  ammonia  would  be  evaporating  at  a  temperature 
of  practically  0  degrees  F.  To  prevent  the  brine  freezing  against  the 
walls  of  the  evaporator,  its  strength  or  density  should  be  made  to  cor- 
respond with  this,  or  from  95  degrees  to  100  degrees  on  the  salometer. 


REFRIGERATION  125 

In  examining  into  the  causes  of  failure  in  a  plant  to  perform 
its  usual  or  rated  capacity,  it  is  advisable,  unless  there  is  every  evi- 
dence that  the  trouble  is  elsewhere,  to  make  an  examination  of  the 
brine  and  determine  whether  its  strength  and  condition  is  suited  to 
the  duty  to  be  performed. 

AUXILIARY  APPARATUS 

Ammonia  Receiver.  The  ammonia  receiver,  or  storage  tank, 
is  a  cylindrical  shell  with  heads  bolted  or  screwed  on,  or  welded  in 
each  end,  and  provided  with  the  necessary  openings  for  the  inlet 
and  outlet  of  the  ammonia,  purge-valve,  and  gauge  fittings.  They 
may  be  vertical  or  horizontal;  the  former  type  is  generally  used  on 
account  of  the  saving  of  floor  space,  while  the  horizontal  is  necessary 
when  the  condenser  is  located  so  low  as 
to  make  the  flow  of  the  liquid  ammonia 
into  the  vertical  type  impossible.  A  con- 
venient location  for  the  receiver  in  a  plant 
in  which  the  condenser  is  located  above 
the  machine  room,  is  against  the  wall,  or 
at  one  side  of  the  room  on  a  bracket  or 
stand  at  one  side  of  the  oil  interceptor, 
the  sizes  of  the  two  being  generally  the 
same.  They  are  then  more  readily  under 
the  control  of  the  engineer  than  if  at  some 
out  of  the  way  place. 

Fig.  52  illustrates  a  receiver  of  the 
vertical  type  with  the  usual  valves  and 
connections  for  the  proper  equipment. 
The  liquid  ammonia  enters  at  the  top 
and  is  fed  to  the  evaporator  from  the 
side  near  the  bottom.  The  space  below 
this  opening  has  been  provided  for  the 
accumulation  of  scale,  dirt,  or  oil,  and 
means  are  furnished  for  drawing  it  off  rig.  52.  vertical  Type  of 
through  the  purge  valve  in  the  bottom. 

Pipes.  Extra  strong,  or  extra  heavy  pipe  is  the  generally  ac- 
cepted pipe  for  connecting  the  various  parts  of  the  refrigerating 
system.  Wrought-iron  pipe  is  generally  preferred  to  steel.  Fre- 


126 


REFRIGERATION 


quently,  however,  and  particularly  for  the  evaporating  or  low-pres- 
sure side  of  the  system,  a  special  weight  or  grade  of  pipe  is  used, 
also  standard  or  common  pipe  is  sometimes  employed  for  this  pur- 
pose. Without  knowing  the  particular  conditions  under  which  this 

is  to  be  used,  or  the  rela- 
tive value  of  the  material, 
or  manner  in  which  the 
pipe  is  made,  it  is  always 
better  to  use  and  insist  on 
having  the  standard  extra 
strong  grade.  The  threads 
should  be  carefully  cut  with 
a  good  sharp  die,  making 
sure  that  the  top  and  bot- 
tom of  the  threads  are 
sharp  and  true.  With  this 
precaution,  and  an  equally 
good  thread  in  the  fitting, 
it  is  not  difficult  to  form  a 
good  and  lasting  joint. 
Particular  care  should  also 
be  taken  that  the  pipe 
screws  into  the  fitting  the 
proper  distance,  and  forms 
a  contact  the  entire  length, 
rather  than  to  screw  up 
against  a  shoulder  without 
a  perfect  fit  in  the  thread. 
This  latter  often  causes 
leaky  joints  some  time  after  the  plant  has  been  operated;  the  tem- 
porary joint  formed  either  by  screwing  in  too  deep  against  the 
shoulder,  or  by  ill-fitting  threads,  very  often  passes  the  test,  and  is 
used  for  some  time  until,  after  the  alternate  effects  of  heat  and 
cold,  and  the  chemical  action  of  the  ammonia  cause  it  to  break  out. 
It  is  a  safe  rule  that  no  amount  of  solder  or  other  doctoring  that  is 
not  backed  up  by  a  good  fitting  thread  to  support  it  can  make 
an  ammonia  joint.  This  is  particularly  true  of  the  discharge  or 
compression  side  of  the  plant. 


Fig.  53.    Boyle  Union. 


REFRIGERATION  127 

The  manner  of  making  these  joints  may  be  divided  into  those 
having  a  compressible  gasket  between  the  thread  on  the  pipe  and 
the  fitting  into  which  it  screws,  and  the  screwed  joint  formed  by  a 
threaded  pipe  screwed  into  a  tapped  flange  or  fitting.  The  latter 
may  be  divided  into  those  having  a  soldered  joint,  or  "one  in  which 
the  union  is  formed  by  the  threads  only,  with  some  of  the  usual 
cements  to  assist  in  making  a  tight  joint. 

The  two  most  prominent  types  of  gasket  fittings  are  shown  in 
Figs.  53  and  54.  The  former  is  known  in  this  country  as  the  Boyle 
Union,  and  is  extensively  used.  As  will  be  observed,  the  drawing 
together  of  the  two  glands  by  the  bolts,  compresses  the  gaskets, 


Fig.  54.    Gland  Type  of  Union. 

usually  rubber,  against  the  threaded  sides  of  the  pipe,  the  bottom 
and  sides  of  the  recess  in  the  flanges,  and  the  edges  of  the  ferrule  be- 
tween the  two  gaskets. 

Figure  54  represents  a  union  or  joint  quite  frequently  used, 
although  not  as  commonly  as  the  former.  In  this  the  pipe  is  threaded 
and  screwed  into  the  body  of  the  fitting,  in  such  a  way  that  it  does 
not  form  an  ammonia-tight  joint;  leakage  is  prevented  by  a  pack- 
ing ring  compressed  by  the  gland  against  the  pipe  thread  and  the 
walls  of  the  recess. 

In  Fig.  55 — a  type  of  ammonia  coupling — the  contact  between 
the  pipe  and  fitting  is  made  to  withstand  the  leakage  of  the  gas  with- 
out the  aid  of  packing  or  other  material  other  than  solder  or  some  of 
the  usual  cements;  the  two  flanges  are  bolted  together  with  a  tongue 


128 


REFRIGERATION 


and  grooved  joint  having  a  soft  metal  gasket.     This  makes  a  per- 
manent and  durable  fitting. 

Other  fittings  of  the  class — as  ells,  tees,  and  return  bends — are 
usually  provided  with  one  of  the  above  methods  of  connecting  with 
the  system,  and  the  different  types  described  may  be  obtained  of 
the  builders  of  refrigerating  machines. 

Valves.     The  valves  for  the  ammonia  system  of  a  refrigerating 
plant  are  of  special  make  and  construction,  being  of  steel  or  semi- 
steel,  with  a  soft  metal  sent  which  may  be  renewed  when  worn,  and 
metal  gaskets  between  the  bonnets  and 
flanges. 

The  usual  types  are  globe,  angle, 
and  gate,  subdivided  into  screwed  and 
flanged.  Fig.  56  is  a  generally  adopted 
type  of  the  flanged  globe  ammonia 
valve,  while  Fig.  57  represents  the 
angle  valve  of  the  same  construction. 
This  seems  to  represent  the  best  ele- 
ments of  a  durable  and  efficient  valve. 
For  a  valve  or  cock  requiring  a  fine 
adjustment,  as  is  frequently  the  case 
in  direct-expansion  systems,  particu- 
larly where  the  length  of  the  evap- 
orating coil  or  system  is  short,  a  V-- 
shaped opening  is  desirable.  Fig.  58 
represents  a  cock  for  this  purpose 
which  will  be  found  to  be  effective 
and  meet  the  most  exacting  require- 
ments. 

Pressure  Gauges.  Two  gauges  are  necessary  for  an  ammonia 
plant  of  a  single  system;  one  to  indicate  the  discharge  or  condensing 
pressure,  and  one  for  the  evaporator  or  return  gas  pressure  to  the 
compressors. 

Owing  to  the  action  of  ammonia  on  brass  and  copper,  the  gauges 
for  this  purpose  differ  from  the  ordinary  pressure  gauge  in  that  it 
is  made  with  a  tube  and  connections  of  steel  instead  of  brass,  and  this 
construction  is  the  general  choice  of  gauge  makers;  in  other  respects 
the  construction  is  similar.  For  machines  of  small  capacity  instru- 


Fig.  55.    Metal  Gasket  Coupling. 


REFRIGERATION 


123 


Fig.  56.    Ammonia  Globe  Valve. 


Fig.  57.    Ammonia  Angle  Valve. 


530 


REFRIGERATION 


ments  with  6-inch  dials  are  common,  while  for  larger  plants  8-inch 
is  the  generally  adopted  size.  The  graduation  for  the  high-pressure 
gauge  is  usually  to  300  pounds  pressure, 
and  if  a  compound  gauge  is  used,  it  is 
made  to  read  to  a  vacuum  also.  This 
latter  is  only  needed  on  certain  occasions 
and  frequently  omitted  from  the  high- 
pressure  gauge.  Owing  to  the  necessity 
of  removing  the  contents  of  the  system 
at  certain  times,  and  usually  through  the 
evaporating  side  of  the  plant,  the  gauge 
for  this  portion  of  the  system  is  graduated 
to  read  from  a  vacuum  to  120  pounds 
pressure. 

In  connecting  the  gauges  to  the  system, 
it  is  customary  to  locate  the  opening  in 
the  discharge  and  return  gas  lines  near 
the  machine  within  the  engine  room, 
placing  a  stop  valve  at  some  convenient 
point  and  carrying  a  line  of  j-  or  ^-inch 
extra  strong  pipe  to  the  gauges,  making 
the  joints  with  the  usual  ammonia  unions. 
On  account  of  the  possibility  of  leakage 
of  ammonia  gas  from  the  gauge  tube,  it 
is  often  considered  advisable  to  fill  the 
g.iuge  pipe  with  oil — of  the  kind  us£d  for 
lubricating  the  ammonia  compressor — for 
Fig  58.  v-pon  Expansion  cock.  a  short  distance  above  the  gauges,  upon 
which  the  pressure  of  the  gas  will  act, 

causing  the  gauge  to  move  properly  but  without  allowing  the  ammonia 
gas  to  enter  the  gauge.  This  is  an  application  of  the  same  principle 
as  the  steam  syphon  or  bent-pipe  arrangement  in  use  with  steam 
gauges,  for  the  purpose  of  keeping  the  heat  and  action  of  steam  from 
the  gauge  mechanism  by  the  retaining  of  water  in  the  gauge  con 
nection. 

Other  gauges  used  about  the  refrigerating  plant  are  of  the 
ordinary  pressure  or  vacuum  types  and  do  not  need  a  special  descrip- 
tion, as  their  construction  and  manner  of  applying  to  the  different 


REFRIGERATION  131 

parts  of  the  system  are  well  known  to  the  engineer.  It  may  be 
well,  however,  to  caution  the  user  on  the  importance  of  testing  the 
gauges  often  enough  to  be  sure  they  are  accurate,  as  serious  damages 
may  result  from  a  wrong  indication  of  pressure. 

METHODS  OF  REFRIGERATION 

Various  systems  are  in  use  for  applying  the  cooling  effect  pro- 
duced by  a  refrigerating  machine  in  general. work  and  in  the  special 
applications  of  refrigeration.  All  systems  may  be  classified  as  either 
direct — in  which  the  gas  is  expanded  in  pipes  located  so  as  to  permit  of 
direct  abstraction  of  heat  from  the  bodies  to  be  cooled;  or  indirect — • 
in  which  brine  is  cooled  and  then  circulated  in  pipes,  or  by  other 
means,  so  as  to  absorb  heat  from  the  bodies  it  is  desired  to  cool. 
Methods  of  making  and  cooling  brine  have  been  described  and  it  is 
only  necessary  to  provide  a  brine  pump  and  the  necessary  brine 
piping.  The  pump  should  be  bronze  fitted  and  the  pipe  should  be 
of  wrought  iron.  In  some  cases  cold  brine  is  made  to  cool  air  and 
the  air  is  circulated  through  the  cold  stores.  Direct  refrigeration 
is  applied  by  two  methods,  the  most  general  being  simple  evaporation 
oj  liquid  in  the  pipes,  there  being  nothing  but  gas  in  the  piping,  as 
the  supply  of  liquid  is  regulated  "by  the  expansion  valve.  In  the 
other  method — the  so-called  flooded  system — the  pipes  or  evaporators 
are  almost  full  of  liquid,  or  at  least  have  the  inner  surfaces  wet. 
Regulation  is  effected  by  the  inlet  valve  and  the  gas  trap  of  special 
design  on  the  outlet,  this  trap  being  arranged  to  return  the  gas  to  the 
compressor  and  at  the  same  time  guard  against  allowing  the  liquid 
to  reach  the  suction  of  the  machine  in  any  quantity  that  might  be 
dangerous. 

Of  course  in  the  wet  system  of  operation  devised  by  Prof.  Linde 
a  certain  amount  of  liquid  is  passed  into  the  suction,  but  this  is  and 
must  be  under  entire  control.  There  are  reasons  for  and  against  each 
of  the  two  methods  of  applying  refrigeration,  but  generally  the  indirect 
or  brine  system,  is  best  for  small  plants,  while  large  plants  should 
use  the  direct-expansion  system.  The  chief  reason  for  retaining 
the  brine  system  in  large  plants  thus  far  has  been  the  fear  of  ammonia 
leaks  that  mean  damage  to  goods  in  store.  Such  leaks  are  com- 
paratively rare  where  reasonably  good  pipe  work  is  used,  and  the  man 
who  uses  any  other  kind  of  piping  deserves  to  foot  up  the  loss  rather 


132  PEFIUGEPATION 

than  be  behind  the  times  with  his  whole  system.  Small  plants 
must  use  brine  to  guard  against  shut-downs  as  the  refrigeration  stored 
in  a  comparatively  large  body  of  brine  is  of  considerable  value  in 
keeping  temperatures  down  at  such  times.  Also  the  small  machine 
may  be  shut  down  at  night  and  the  brine  pump  kept  going  to  circulate 
the  brine,  thus  effecting  considerable  saving  in  operation  costs.  The 
same  results  can  be  had  to  a  certain  extent  by  having  shallow  pans 
of  brine  placed  over  the  pipes  in  the  coolers.  Where  very  low  tem- 
peratures are  required,  as  in  the  case  of  fish  and  poultry  freezers,  the 
direct-expansion  system  is  a  necessity. 

PROPORTION  BETWEEN  THE  PARTS  OF  A  REFRIG- 
ERATING PLANT 

There  is  necessarily  a  certain  ratio  or  proportion  between  the 
several  parts  of  a  refrigerating  plant,  as  there  is  between  the  boiler 
engine,  and  parts  of  a  steam  or  power  plant,  in  order  to  obtain  the 
most  economical  results.  It  is  first  necessary  that  the  evaporator 
be  provided  with  heat-transmitting  surface  sufficient  to  conduct 
284,000  B.  T.  U.  from  the  brine  to  the  ammonia,  for  each  ton  of 
refrigeration  to  be  performed.  Without  going  into  a  theoretical 
calculation  of  this  amount,  we  shall  state,  in  both  lineal  feet  of  pipe 
and  square  feet  of  pipe  surface,  the  commercial  sizes  and  amounts 
ordinarily  in  use. 

The  coil  surface  in  a  brine-tank  system  of  refrigeration,  should 
contain  approximately  50  square  feet  of  external  pipe  surface,  to 
each  ton  in  refrigerating  capacity  of  the  plant,  when  it  is  to  be  operated 
at  a  temperature  of  15  degrees  F.  This  is  an  ample  allowance  and 
will  be  found  under  general  working  conditions  to  give  readily  the 
required  capacity.  While  tests  have  been  made  in  which  40  square 
feet  of  pipe  surface  has  been  found  sufficient  for  one  ton  of  refrig- 
eration, it  will  be  safer  to  use  the  former  amount,  owing  to  the  varied 
conditions  under  which  a  plant  may  be  operated.  This  would  amount 
in  round  figures  to  150  lineal  feet  of  1-inch  pipe,  115  feet  of  1^-inch 
100  feet  of  H-inch,  or  80  feet  of  2-inch  pipe.  For  each  ton  in  re- 
frigerating capacity,  the  pipe  surface  of  the  brine  tank  should  vary 
from  40  to  60  cubic  feet,  depending  on  the  amount  of  storage  ca- 
pacity desired. 

The  submerged   type  of  ammonia   condenser  should   contain 


REFRIGERATION  133 

approximately  35  square  feet  of  external  surface  which  nearly  cor- 
responds to  100  lineal  feet  of  1-inch,  80  feet  of  1^-inch,  70  feet  of 
1  ^-inch,  and  56  feet  of  2-inch  pipe. 

The  atmospheric  type  of  condenser  should  contain  30  square 
feet  of  external  pipe  surface  which  corresponds  to  87  lineal  feet  of 
1-inch,  69  feet  of  l|-inch,  60  feet  of  H-inch,  and  48  feet  of  2- 
inch  pipe. 

The  double-pipe  type  of  condenser,  as  usually  rated,  contains 
7  square  feet  of  external  pipe  surface  for  the  water  circulating  pipe 
and  about  10  square  feet  of  internal  pipe  surface  for  the  outer 
pipe,  and  corresponds  to  approximately  20  lineal  feet  each  of  \\- 
inch  and  2-inch  sizes  for  each  ton  of  refrigerating  capacity. 

The  above  quantities  are  based  on  a  water  supply  of  average 
temperature — 60  degrees — and  quantity.  In  cases  of  a  limited  supply 
or  higher  temperature  than  ordinary,  a  greater  amount  should  be  used. 

The  ammonia  compressor  should  be  of  such  dimensions  that 
it  will  take  away  the  gas  from  the  brine  cooler,  evaporating  coils, 
or  system,  as  rapidly  as  formed  by  the  evaporation  of  the  liquid 
ammonia;  and  unless  the  temperature  at  which  the  plant  is  to  be 
operated  be  known,  it  is  impossible  to  determine  the  volume  of 
gas  to  be  handled  and  the  necessary  size  of  the  compressor. 

As  stated  before,  the  unit  of  a  refrigerating  plant  is  usually 
expressed  in  tons  of  refrigeration  equal  to  284,000  B.  T.  U.  Up 
to  the  present  time,  however,  a  standard  temperature  at  which  this 
duty  shall  be  performed  has  never  been  established,  and  therefore 
the  rating  of  a  machine,  evaporator,  or  condenser  by  tonnage  is  a 
merely  nominal  one  and  misleading  to  the  purchaser,  a  range  of  as 
great  as  50  per  cent  very  often  existing  in  the  tenders  for  certain  con- 
tracts. Upon  the  basis,  however,  of  the  average  temperature  required 
of  the  refrigerating  apparatus  that  of  15  degrees  F.  is  probably  the 
mean;  and  at  this  temperature  in  the  outgoing  brine,  it  is  necessary 
to  take  away  from  the  evaporator  nearly  7,000  cubic  inches  of  gas  per 
minute  for  each  ton  of  refrigeration  developed  in  twenty-four  hours. 
This  may  be  considered  as  a  fair  basis  for  the  rating  of  the  displace- 
ment of  the  compressor  or  compressors  of  the  plant,  unless  a  specific 
temperature  is  stated  at  which  the  plant  is  to  operate.  At  0  degrees 
F.  it  is  necessary  to  calculate  on  approximately  9,000  cubic  inches, 
while  at  28  degrees  F.  about  5,000  will  be  the  required  amount. 


134  REFRIGERATION 

For  example,  if  we  have  two  single-acting  compressors  12  inches 
diameter  by  24  nches  stroke,  operating  at  70  revolutions  per  minute, 
we  would  have  113.09  (inches,  area  of  12-inch  circle)  X  24  (inches 
stroke)  X  2  (number  of  compressors)  X  70  (revolutions)  -f-  7,000 
(cubic  inches  displacement  required)  =  54.28  (tons  refrigeration 
per  24  hours  of  operation) ;  while  if  the  same  machine  is  to  be  operated 
at  or  near  a  temperature  of  zero  and  we  divide  the  product  by  9,000, 
we  have  a  capacity  of  42.22  tons  only,  in  the  same  length  of  time. 
The  above  quantities  are  given  as  approximate  only,  but  they  have 
been  deduced  from  the  average  results  obtained  from  years  of  prac- 
tice and  will  be  found  reliable  under  average  conditions.  It  is  to  be 
hoped,  however,  that  a  standard  will  soon  be  adopted  which  will 
rate  machines  or  plants  by  cubic  inches  displacement  at  a  certain 
number  of  revolutions  or  a  stated  piston  speed,  and  the  cooling  of  a 
certain  number  of  gallons  of  brine  per  minute  through  a  certain 
range  of  temperature. 

TESTING  AND  CHARGING 

Having  described  the  different  parts  of  the  refrigerating  plant 
and  their  relations  to  one  another,  let  us  consider  the  process  of 
testing  and  charging,  or  introducing  the  ammonia  into  the  system. 
After  the  connections  are  made  between  the  different  parts,  whether 
the  system  is  brine  or  direct  expansion,  it  is  necessary  to  introduce 
air  pressure  into  it  to  determine  the  state  of  the  joints.  This  may 
be  done  in  sections  or  altogether.  It  is  customary,  however,  to  put 
a  higher  pressure  on  the  compression  side  of  the  plant  than  on  the 
evaporator  owing  to  the  difference  in  the  pressure  carried  in  opera- 
tion. Adjacent  to  each  compressor  is  placed  a  main  stop  valve,  on 
both  the  inlet  and  outlet  sides,  while  on  either  side  of  these  it  is 
customary  to  place  a  by-pass  or  purge  valve. 

Before  starting  the  compressor,  the  main  stop  valve — or  valves 
if  there  be  two — on  the  inlet  or  evaporating  side  of  the  compressor, 
is  closed,  the  small  valve  between  the  compressor  and  the  main 
stop  valve  opened,  and  all  of  the  other  valves  on  the  system  opened 
except  those  to  the  atmosphere.  The  compressor  may  then  be 
started  slowly,  air  being  taken  in  through  the  small  by-pass  valves 
and  compressed,  into  the  entire  system.  It  is  well  to  raise  a  few 
pounds  pressure  on  the  entire  system  before  admitting  water  into 


REFRIGERATION  135 

the  compressor  water  jackets  or  other  parts  of  the  system,  because 
if  a  joint  were  improperly  made  up,  it  would  be  possible  for  the 
water  to  enter  the  compressors,  or  coils  of  the  condenser  or  evap- 
orator, and  serious  damage  or  loss  of  efficiency  in  the  plant  occur, 
which  it  might  be  impossible  to  locate  afterwards.  While  if  pres- 
sure exists  within  the  system  when  the  water  is  admitted,  its  en- 
trance into  the  coils  or  system  is  impossible  while  the  pressure  exists, 
and  the  leak  is  at  once  visible  and  may  be  remedied  before  proceed- 
ing further. 

In  starting  the  test  it  is  also  well  to  try  the  two  pressure  gauges 
and  see  that  they  agree  as  to  graduation;  as  it  has  happened  that 
owing  to  a  leakage  between  the  discharge  pipe  and  the  high  pres- 
sure gauge,  an  enormous  pressure  has  been  pumped  into  the  system 
causing  it  to  explode,  with  a  consequent  result  of  loss  of  life 
and  property.  If,  however,  the  pressures  are  found  to  be  equal  on 
the  two  gauges  it  is  safe  to  assume  that  they  are  recording  properly 
and  their  connections  are  tight.  After  these  preliminaries  it  is  safe 
to  put  an  air  pressure  of  300  pounds  on  the  compression  side  of  the 
plant,  care  being  taken  to  operate  the  compressor  slowly,  not  rais- 
ing the  temperature  of  the  compressed  air  too  much,  as,  with  the 
utmost  care  in  making  up  joints  and  in  selecting  material,  certain 
weaknesses  may  exist  and  under  such  high  pressure  it  is  well  to  pro- 
ceed with  caution. 

After  the  desired  pressure  has  been  reached,  the  entire  system 
should  be  gone  over  repeatedly  until  it  is  absolutely  certain  that  it 
is  tight.  Parts  which  can  be  covered  with  water,  such  as  a  sub- 
merged form  of  condenser  or  brine  tank  with  evaporating  coils, 
should  be  so  covered  that  the  entire  surface  may  be  gone  over  at  once 
and  with  almost  absolute  certainty.  The  slightest  leakage  will 
cause  air  bubbles  to  ascend  to  the  surface.  This  leakage  may  be 
traced  by  allowing  the  water  to  flow  from  the  tank  while  the  air 
pressure  is  still  on  the  coils  or  system,  marking  the  points  where 
the  bubbles  occur.  The  coils  may  then  be  taken  up  or  repaired 
when  empty.  For  parts  which  cannot  be  covered  with  water,  it  is 
customary  to  apply  with  a  brush  a  lather  of  such  consistency  that  it 
will  not  run  off  too  readily;  upon  coming  in  contact  with  a  leak,  soap 
bubbles  are  formed,  and  by  tracing  to  the  starting  point  the  leak 
may  be  located.  After  the  compression  system  has  been  subjected 


136  REFRIGERATION 

to  a  pressure  of  300  pounds  and  found  to  be  tight,  the  air  may  be 
admitted  through  the  liquid  ammonia  pipe  to  the  evaporating  side 
of  the  plant,  care  being  taken  that  the  pressure  does  not  rise  above 
the  limit  of  the  gauge — which,  as  previously  stated,  is  usually  120 
pounds — and  the  same  process  of  testing  as  applied  to  the  opposite 
side  of  the  plant  gone  over. 

Many  engineers  require  the  vacuum  test  as  well  as  the  fore- 
going, and  although  if  the  former  is  gone  over  thoroughly,  there  can 
be  little  chance  of  leakage  afterwards,  it  is  better  to  be  over-exacting 
than  otherwise  in  the  matter  of  testing  and  preparation  of  the  plant, 
thus  preventing  the  possibility  of  leaks  that  may  prove  disastrous. 
Open  the  main  stop  valves  on  the  inlet  line  and  close  the  main  valves 
above  the  compressor  on  the  discharge  line,  closing  the  by-pass 
valves  in  the  suction  line,  and  opening  those  in  the  discharge  line 
between  the  main  stop  valve  and  the  compressor.  Have  all  the 
other  valves  on  the  system  open  as  before  for  testing.  Starting  the 
compressor  draws  in  the  air,  filling  the  system  through  the  com- 
pressor and  discharging  it  at  the  small  valve  left  open.  Assum- 
ing the  system  to  be  tight,  continuing  the  operation  will  finally  ex- 
haust the  air,  or  nearly  so,  when  the  small  valves  should  be  closed 
and  the  pressure  gauges  watched  to  determine  whether  or  not  leakage 
exists. 

Assuming  that  the  system  and  apparatus  is  tight  in  every  par- 
ticular and  that  it  is  otherwise  ready  to  be  placed  in  operation,  we 
are  now  ready  to  charge  the  ammonia  into  the  plant. 

If  the  air  has  been  exhausted  from  the  system  in  testing,  this 
usual  step  need  not  be  taken  before  charging,  and  it  is  only  neces- 
sary to  put  the  machine  in  proper  condition  to  resume  the  pump- 
ing of  the  gas,  and  to  attach  a  cylinder  of  ammonia  to  the  charging 
valve  to  enable  the  refrigeration  to  be  commenced.  The  main  stop 
valves  above  the  compressor,  which  were  closed  in  expelling  the  air, 
should  now  be  opened,  and  by-pass  and  other  valves  to  the  atmosphere 
closed.  Close  the  outlet  valve  from  the  ammonia  receiver  and  start 
the  machine  slowly,  at  the  same  time  opening  the  feed  valve  between 
the  drum  of  ammonia  and  the  evaporator.  The  anhydrous  liquid  am- 
monia will  flow  into  the  evaporator  through  the  regular  supply  pipe, 
the  gas  resulting  from  evaporation  being  taken  up  by  the  compress- 
ors and  discharged  into  the  condenser  and  finally  settling  down  into 


REFRIGERATION  137 

the  receiver,  when  a  sufficient  quantity  has  been  introduced  to  form 
a  supply  there.  Upon  closing  the  valves  between  the  drum  from 
which  the  supply  is  being  drawn,  and  opening  the  outlet  valve  from 
the  receiver,  the  process  of  refrigei  ation  by  the  compression  system 
is  regularly  in  operation. 


6  'i 


REFRIGERATION 

PART  III 


OPERATION  AND   MANAGEMENT  OF  THE  PLANT 

Assuming  that  the  plant  has  been  properly  erected,  tested,  and 
charged  with  ammonia  of  a  good  quality — and  if  a  brine  system, 
with  brine  of  proper  strength  or  density,  as  already  explained — it 
only  remains  to  keep  the  system  or  plant  in  that  condition.  As  all 
forms  of  mechanism  are  liable  to  disarrangement  and  deterioration 
from  various  causes,  repairs  and  corrections  from  time  to  time  must 
be  made  to  keep  them  in  good  condition.  Let  us  now  consider  the 
most  important  points  requiring  attention. 

It  is  absolutely  necessary  for  the  good  working  of  any  type  of 
plant  or  apparatus  that  it  be  kept  clean.  As  a  steam  boiler  must 
be  clean  to  obtain  the  full  benefit  of  the  fuel  consumed,  so  must 
the  surfaces  of  the  condenser  and  evaporator  be  clean  to  obtain  the 
proper  results  from  the  condensing  water  and  evaporation  of  the 
ammonia  or  other  refrigerant. 

For  satisfactory  work,  the  system  should  be  purged  of  any  foreign 
element  present  in  the  pipes,  such  as  air,  water,  oil,  or  brine.  For- 
eign matter  is  the  most  common  among  internal  causes  for  loss  of 
efficiency,  and  the  valve  openings  which  have  been  shown  and  de- 
scribed should  be  used  for  cleaning  the  system. 

Oil  is  used  as  a  lubricant  in  nearly  if  not  quite  all  compressors, 
and  the  quantity  should  be  the  least  amount  that  will  lubricate  the 
surfaces  and  prevent  undue  wear.  This  is  considerably  less  than 
the  average  engineer  is  inclined  to  think  necessary,  and  consequently 
a  coating  forms  on  the  walls  of  the  pipes  or  other  surfaces  of  the  con- 
densing or  evaporating  systems,  and  a  proportionate  decrease  in  the 
duty  is  obtained.  It  is  also  necessary  that  the  oil  be  of  such  a  nature 
that  it  is  not  saponified  by  contact  with  the  ammonia.  Such  a  change 
would  choke  or  clog  the  pipes,  coating  their  surfaces  with  a  thick 
paste  which  causes  a  corresponding  loss  as  the  amount  increases. 


140  REFRIGERATION 

The  purge  valve  in  the  bottom  of  the  oil  interceptor  may  be  opened 
slightly  about  once  each  week,  and  the  oil  discharged  from  the  com- 
pressors drawn  off  into  a  pail  or  can,  unless  a  blow-off  reservoir  is 
provided.  After  the  gas  with  which  it  is  charged  has  escaped,  the 
oil  should  be  practically  the  same  as  when  fed  into  the  compressors. 
If,  however,  the  oil  is  not  of  the  proper  quality  it  will  remain  thick 
and  pasty,  or  gummy,  showing  it  to  have  been  affected  by  the  am- 
monia. Its  use  should  not  be  continued. 

By  opening  the  purge  valves,  which  are  usually  provided  at 
the  bottom  manifold  or  header  of  the  brine  tank  and  the  bottom 
head  of  the  brine  cooler,  oil  or  water,  if  there  is  any  in  that  part  of  the 
system,  may  be  drawn  off.  These  valves,  however,  should  not  be 
opened  unless  there  is  some  pressure  in  that  part  of  the  system,  as 
air  would  be  admitted  if  the  pressure  within  the  apparatus  is  below 
that  of  the  atmosphere.  Air  may  enter  the  system  through  a  variety 
of  causes  and  its  presence  is  attended  with  higher  condensing  pres- 
sure and  a  falling  off  in  the  amount  of  work  performed.  For  the 
removal  of  air  from  the  apparatus,  a  purge  valve  is  placed  at  the 
highest  point  in  the  condenser  or  discharge  pipe  from  the  compress- 
ors near  the  condenser,  which  may  be  tried  when  the  presence  of 
air  or  foreign  gases  is  suspected.  This  should  be  done  after  the 
compressor  has  been  stopped.  When  the  condenser  has  fully  cooled 
and  the  gases  separated,  a  small  rubber  hose  or  pipe  may  be  carried 
into  a  pail  of  water  and  the  purge  valve  or  valves  slightly  opened. 
If  air  or  other  gases  exist  in  the  system,  bubbles  will  rise  to  the  surface 
of  the  water  so  long  at  it  is  escaping;  while,  if  ammonia  is  being 
blown  off,  it  will  be  absorbed  in  the  water  and  not  rise  to  the  sur.ace. 

To  prevent  the  possibility  of  air  getting  into  the  system  the 
evaporating  pressure  should  never  be  brought  below  that  of  the 
atmospheric,  or  0  degree  on  the  gauge,  as  at  such  times,  with  the 
least  leakage  at  any  point,  it  is  sure  to  enter.  Should  it  become 
necessary  to  reduce  the  pressure  below  that  point,  it  is  well  first  to 
tighten  the  compressor  stuffing  boxes  and  allow  the  pressure  to  remain 
below  0  degree  only  the  shortest  possible  time,  as  not  only  air  may 
enter,  but  if  it  be  the  brine  system  and  a  leak  exists,  brine  also  will  be 
drawn  in. 

From  the  foregoing  it  is  evident  that  in  order  to  obtain  satis- 
factory results,  the  interior  of  the  system  must  be  kept  clean  by 


REFRIGERATION  141 

purging  at  the  different  points  provided  for  this  purpose;  and  it 
need  only  be  added  in  this  connection,  that  when  the  presence  of  oil 
or  moisture  becomes  apparent  in  any  quantity,  the  coils  or  other 
parts  should  be  disconnected  and  blown  out  with  steam  until  thor- 
oughly clean,  and  afterwards  with  air  to  make  certain  that  conden- 
sation from  the  steam  does  not  remain.  After  this  the  parts  may 
again  be  connected  and  tested  ready  for  operation. 

If  the  plant  be  a  brine  system,  it  is  necessary  that  the  brine  be 
maintained  at  a  proper  strength  or  density  to  obtain  satisfactory 
results;  for  if  it  becomes  weakened,  it  freezes  on  the  surfaces  of  the 
pipes  or  evaporator,  thereby  acting  as  an  insulator  and  preventing 
the  rapid  transmission  of  heat  through  the  walls. 

It  is  of  great  importance  to  know  at  all  times  whether  or  not 
the  gas  taken  into  the  compressors  is  fully  discharged  into  the  con- 
denser, as  the  slightest  loss  at  this  point  is  certain  to  make  itself  felt 
in  the  operation  of  the  plant.  The  compressor  and  valves  seldom 
need  be  taken  apart  to  determine  their  operation.  The  engineer 
should  be  able  to  discern  when  the  compressors  are  working  at  their 
best,  by  placing  the  hand  on  the  inlet  and  outlet  pipes  or  on  the  lower 
part  of  the  compressors  so  as  to  detect  slight  change  from  normal 
temperature.  Should  the  inlet  pipe  to  one  compressor  be  warmer 
than  that  to  the  other  (of  a  pair),  or  the  frost  on  the  pipe  from  the 
evaporator  reach  nearer  one  compressor  than  the  other,  it  is  then 
certain  that  the  one  with  the  higher  temperature,  or,  from  which 
the  frost  is  farthest,  is  not  working  properly  or  doing  as  much  duty 
as  the  other;  and  it  is  equally  certain  that  some  condition  exists 
which  prevents  the  complete  filling  and  discharge  of  its  contents; 
possibly  it  has  more  clearance  or  leaky  valves. 

The  most  common  difficulties  experienced  with  ammonia  con- 
densers are  those  of  keeping  the  external  surfaces  clean  and  free 
from  deposits,  and  preventing  the  accumulation  of  air  or  foreign  gases 
within.  Deposits  on  the  surface  are  usually  of  two  kinds — one, 
a  soft  deposit  which  may  be  washed  off  with  a  brush  or  wire 
scraper  such  as  is  used  for  cleaning  castings  in  a  foundry;  the  other, 
a  hard  deposit  which  must  be  loosened  with  a  hammer  or  scraper. 
It  is  hardly  necessary  to  explain  in  detail  the  methods  employed  in 
cleaning  the  condenser  as  this  is  a  matter  that  each  engineer  will  be 
able  to  accomplish  in  his  own  way.  It  should  not,  however,  be  over- 


142  REFRIGERATION 

looked,  and  with  a  condensing  pressure  higher  than  ordinary,  this 
should  be  the  first  point  to  be  examined  after  the  water  supply. 

Air  and  foreign  gases  due  to  decomposition  of  the  ammonia  or 
other  causes,  find  their  way  into  the  condenser  and  make  themselves 
manifest  generally  in  a  higher  condensing  pressure,  or  a  falling  off 
in  the  duty  to  be  obtained  from  the  plant.  They  should  be  blown 
off  through  the  purge  valve  at  the  top  of  the  condenser  in  the  man- 
ner already  described. 

It  is  possible,  through  leakage  of  the  coils  or  other  parts  of  the 
apparatus,  that  the  ammonia  may  become  mixed  with  brine  or  water, 
thereby  retarding  its  evaporation  and  interfering  with  the  proper  or 
usual  operation  of  the  plant.  If  this  is  suspected,  a  sample  may  be 
drawn  off  into  a  test  glass  through  the  charging  valve  or  purge  valve 
of  the  brine  tank  or  ammonia  receiver  and  allowed  to  evaporate, 
in  which  case  the  water  or  brine  will  remain  in  the*  glass  and  the  relative 
amount  be  determined.  Through  careful  evaporation  and  con- 
tinued purging  of  the  evaporator  at  intervals,  this  may  in  time  be 
eliminated,  and  care  should  be  taken  to  prevent  future  recurrence. 

Loss  of  Ammonia.  This  should  be  constantly  guarded  against. 
It  is  watchfulness  which  determines  between  a  wasteful  and  an 
economical  plant  in  this  particular,  and  the  engineer  who  allows  the 
slightest  smell  of  ammonia  to  exist  about  the  plant  is  certain  to  be 
confronted  with  excessive  ammonia  bills;  while  he  who  is  constantly 
on  the  alert  and  never  rests  until  his  plant  is  as  free  from  the  smell 
of  ammonia  as  an  ordinary  engine  room,  will  be  referred  to  as  the 
one  who  ran  such  and  such  a  plant  without  addition  of  more  ammonia 
for  so  many  years. 

The  escape  of  ammonia  into  the  atmosphere  is  readily  detected; 
but  where  a  leakage  occurs  in  a  submerged  condenser,  brine  tank, 
or  brine  cooler  it  is  necessary  to  examine  the  surrounding  liquid  to 
determine  whether  or  not  it  exists.  For  this  purpose  various  agents 
are  employed,  and  may  be  obtained  of  druggists  or  from  the  manu- 
facturers of  ammonia.  Red  litmus  paper  when  dipped  into  water 
or  brine  contaminated  with  ammonia  will  turn  blue.  Nessler's 
solution  causes  the  affected  water  to  turn  yellow  and  brown,  while 
phenolphthalen  causes  a  bright  pink  color  with  the  slightest  amount 
of  ammonia  present. 

The  stopping  of  a  leakage  of  ammonia  in  the  brine  tank  or 


REFRIGERATION  143 

cooler  may  be  possible  while  the  plant  is  in  operation,  by  shutting 
off  the  coil  in  which  it  occurs,  or,  if  the  point  is  accessible  a  clamp 
and  gasket  may  be  put  in  place  temporarily. 

Purging  and  Pumping  out  Connection.  A  common  cause  of 
failure  to  operate  properly  and  effectively  is  the  introduction  of  some 
foreign  substance  into  the  system.  This  will  be  readily  understood 
and  appreciated  by  engineers  and  those  familiar  with  the  require- 
ments of  a  steam  boiler.  Clean  surfaces  on  the  shell  or  tubes  are 
necessary  for  the  maximum  evaporation  of  water,  or  for  the  transfer 
of  heat  through  the  walls  of  pipe  or  other  forms  of  heat-transmitting 
surface.  The  most  common  difficulty  encountered  in  a  refrigera- 
ting plant  is  oil,  either  in  its  natural  condition,  or  saponified  by  con- 
tact with  the  ammonia,  water,  or  brine.  It  enters  the  system  in 
many  ways;  through  leakage,  condensation  in  blowing  out  the  coils 
or  system,  foreign  gas  arising  from  decomposition  of  the  ammonia 
through  excessive  heat  and  pressure,  or  the  mingling  of  air  which 
may  enter  the  system  through  pumping  out  below  atmospheric  pres- 
sure, or  the  air  may  have  remained  in  the  system  from  the  time  of 
charging,  never  having  been  fully  removed.  It  is  also  probable, 
though  hard  to  determine  with  certainty  owing  to  the  various  con- 
ditions surrounding  the  operation  of  plants,  that  impurities  are  in- 
troduced with  the  ammonia,  either  in  the  form  of  liquid,  gas,  or  air, 
which  afterward  become  impossible  to  condense. 

The  oil  in  a  system  forms  a  covering  or  coating  on  the  evap- 
orating surface  which  acts  as  an  insulation  and  prevents  the  ready 
transfer  of  heat  through  the  walls  of  the  evaporator.  The  presence 
of  water  or  brine  causes  an  absorption  of  a  portion  of  the  ammonia 
into  the  water  or  brine,  forming  aqua  ammonia  which  raises  the 
boiling  point  of  the  ammonia  and  causes  material  loss  in  the  duty. 
Air  or  other  non-condensable  gas  in  the  system,  excludes  an  equ?l 
volume  of  the  ammonia  gas,  thereby  reducing  the  available  condens- 
ing surface  in  that  proportion. 

For  the  purpose  of  cleaning  the  system  and  removing  the  dif- 
ferent impurities  which  may  appear,  purge  and  blow-off  valves  and 
connections  are  provided.  One  of  these  is  placed  at  or  near  the 
bottom  of  the  oil  interceptor,  which  is  located  between  the  com- 
pressors and  the  condenser;  it  is  used  to  draw  off  the  oil  used  as  a 
lubricant  in  the  compressor  and  which  is  precipitated  to  the  bot- 


144  REFRIGERATION 

torn.  This  oil  should  not  be  allowed  to  accumulate  to  any  great 
extent  as  it  may  be  carried  forward  to  the  condenser  by  the  current 
of  gas. 

If  the  liquid  ammonia  receiver  be  placed  in  a  vertical  position 
it  is  customary  to  place  a  purge  valve  in  the  bottom  for  drawing  off 
oil  or  other  impurities.  The  supply  of  liquid  to  the  evaporator  \s 
taken  off  at  a  short  distance  above  the  bottom  say,  4  to  6  inches. 

The  next  point  for  the  removal  of  impurities  is  at  the  bottom 
of  the  brine  cooler,  or  the  lower  manifold  of  the  coil  system  in  a 
brine-tank  refrigerator.  Tests  at  these  points  may  be  made  as  often 
as  necessary  to  determine  the  state  of  cleanliness  of  the  system.  If  the 
system  is  charged  with  any  of  the  common  impurities,  they  should 
be  blown  out  and  the  system  cleansed  at  the  earliest  possible  mo- 
ment, as  they  cause  a  decided  loss. 

Air  and  foreign  gases  accumulate  in  the  condenser  because  the 
constant  pumping  out  of  the  evaporating  system  tends  to  remove 
them  from  that  part  of  the  system  to  the  condenser.  This  point, 
therefore,  is  the  most  natural  place  for  their  removal.  For  this 
purpose  it  is  customary,  on  the  best  condensers,  to  place  a  header  or 
manifold  at  the  top  at  one  end,  and  connect  each  of  the  sections  or 
banks  with  a  valve  opening.  A  valve  is  also  placed  at  each  end  of 
the  header,  and  a  connection  made  from  one  end  of  this  header  to 
the  return  gas  line  between  the  evaporator  and  the  compressors. 
By  closing  the  stop  valves  on  the  gas  inlet  and  liquid  outlet  of  any 
one  of  the  sections  and  opening  the  purge  or  pumping-out  line  into 
the  gas  line  to  the  compressors,  the  section  or  tank  may  be  emptied 
of  its  contents  for  repairs  or  examination  and  then  connected  up  and 
put  into  service  without  either  shutting  down  the  plant,  or  losing  a 
material  quantity  of  ammonia.  For  purging  of  air  or  gas,  the  valve 
between  this  header  and  the  machine  should  be  closed,  and  the 
valve  on  the  opposite  end  opened  to  the  atmosphere,  the  valves  on 
each  section  in  turn  opened  slightly  while  the  foreign  gases  are  ex- 
pelled. This  process  should  not  be  used  while  the  compressor  is  in 
operation,  as  the  discharge  of  the  ammonia  into  the  condenser  would 
keep  the  gas  churned  to  the  extent  that  it  would  become  impos- 
sible to  remove  the  foul  gases  without  removing  a  considerable  por- 
tion of  the  ammonia  also. 

For  this  reason  it  is  customary  before  blowing  off  the  condenser 


REFRIGERATION  145 

to  stop  the  compressor  and  allow  the  water  to  flow  over  the  condenser 
until  it  is  thoroughly  cooled.  Sufficient  time  should  elapse  for  the 
ammonia  to  liquefy  and  settle  towards  the  bottom,  while  the  air  and 
lighter  gases  rise  to  the  top,  at  which  point  they  may  be  blown  out 
through  the  purge  valve  to  the  atmosphere.  If  doubt  exists  as  to 
whether  ammonia  or  impurities  are  being  blown  out,  attach  a  piece 
of  hose  to  the  end  of  the  purge  valve  and  immerse  its  other  end  in  a 
pail  of  water.  If  it  is  air,  bubbles  will  rise  to  the  surface,  while  if 
it  is  ammonia,  it  will  be  absorbed  into  the  water;  the  mingling  of  the 
ammonia  with  the  water  will  cause  a  crackling  sound,  and  the  tem- 
perature of  the  water  will  increase  owing  to  the  chemical  action. 

ICE=  MAKING  PLANTS 

One  of  the  most  important  applications  of  refrigeration  is  in 
the  production  of  artificial  ice.  Thus  refrigeration,  which  in 
former  times  was  produced  only  by  the  melting  of  ice,  is  now  pro- 
duced artificially  and  used  in  making  ice.  In  order  to  freeze  water, 
it  is  only  necessary  that  its  temperature  be  lowered  to  the  freezing 
point  and  tfre  latent  heat  of  liquefaction  abstracted.  In  practice, 
to  get  rapid  freezing,  the  temperature  of  the  ice  formed  is  carried 
below  the  freezing  point,  so  that  calculations  of  the  heat  to  be  ab- 
stracted must  cover  this.  Assuming  that  the  water  supply  has  a 
temperature  of  60°  F.,  28  B.  T.  U.  will  have  to  be  removed  from  1 
pound  of  water  to  reduce  it  to  freezing  temperature.  Then,  since 
the  latent  heat  of  ice  is  142.65,  this  number  of  heat  units  must  be 
abstracted  to  freeze  the  pound  of  water,  and  since  the  temperature 
of  ice  is  usually  about  20°  F. — or  12  degrees  below  freezing — and 
its  specific  heat  0.5,  we  have  6  B.  T.  U.  to  be  removed  on  this  ac- 
count. Thus  altogether  176.65  B.  T.  U.  must  be  removed  from  one 
pound  of  water  to  freeze  it. 

Of  the  many  more  or  less  impracticable  schemes  that  have  been 
devised  to  freeze  ice,  only  three  are  to  any  extent  in  use  at  the  pres- 
ent time.  These  are  known  as  the  can,  the  plate,  and  the  cell  systems. 
The  latter  is  used  in  England  but  not  to  any  extent  in  the  United 
States,  where  the  great  majority  of  the  plants  are  on  the  can  system 
with  a  few  working  on  the  plate  plan.  Indeed,  the  can  system  is 
most  in  use  the  world  over,  in  spite  of  the  fact  that  there  are  a  num- 
ber of  disadvantages  connected  with  its  use.  As  good  ice  can  be 


146  REFRIGERATION 

made  by  one  system  as  by  the  other  when  both  are  operated  properly, 
but  it  costs  more  to  make  ice  with  the  can  system  owing  to  the  purify- 
ing apparatus  that  must  be  employed  if  the  ice  is  to  be  made  clear 
and  firm.  The  plate  plant  costs  from  30  to  75  per  cent  more  to  con- 
struct and  requires  considerably  larger  buildings  and  more  ground 
space.  This  means  greater  fixed  charges,  but  the  disadvantage  is  offset 
in  part,  at  least,  by  the  fact  that  the  plate  plant  will  make  from  10  to 
14  tons  of  ice  per  ton  of  coal  burned,  while  the  average  for  good  can 
plants  is  from  6  to  8  tons.  The  practical  skill  required  to  operate 
the  two  plants  is  about  the  same,  but  somewhat  more  technical 
knowledge  is  required  in  the  case  of  direct-expansion  plate  plants. 
As  a  rule  it  never  pays  to  build  small  plate  plants  and  in  the 
larger  plants  a  high  grade  of  equipment,  consisting  of  compound 
condensing  engines  and  power-driven  handling  devices,  must  be 
employed  to  get  the  economy  that  will  justify  the  building  of  such  a 
plant.  Such  machinery  requires  a  high  degree  of  skill  for  proper 
operation.  Fixed  charges  and  depreciation  are  greater  with  the 
plate  system.  Where  a  large  plant  is  to  be  operated  by  hydro- 
electric or  other  cheap  power,  it  will  pay  to  build  a  plate  plant, 
the  system  requiring  no  steam  to  freeze  the  water,  as  in  the  case  of 
the  can  plant. 

Can  System.  As  the  name  implies,  this  system  uses  cans  in 
which  the  ice  is  frozen,  the  cans  being  filled  with  water  and  partially 
immersed  in  a  mechanically-cooled  non-freezing  brine  bath.  Freez- 
ing proceeds  from  the  four  sides  and  the  bottom,  and  the  impurities 
in  the  water,  which  have  not  been  removed  during  the  first  stages 
of  the  freezing  process,  are  finally  frozen  into  the  center  of  the 
block.  The  central  opaque  core  formed  in  this  way  is  undesirable, 
and  it  is  to  the  necessity  for  eliminating  it  that  all  the  complica- 
tions of  the  can  system  are  due.  Distilling,  reboiling,  and  filtering 
apparatus  must  be  employed  except  where  porous  opaque  ice  is 
not  particularly  objectionable,  as  in  packing  fish  and  icing  cars.  By 
freezing  ice  at  a  comparatively  high  temperature,  say  25°,  clear  ice 
can  be  made  by  the  can  system  with  natural  water,  but  it  is  not 
practicable  to  use  so  high  a  temperature,  owing  to  the  length  of  time 
required  to  freeze  the  ice  and  the  comparatively  large  tanks  that 
would  have  to  be  employed.  On  this  account  ice  is  frozen  at  from 
12°  to  20°,  the  usual  working  temperature  being  from  14°  to  16°. 


REFRIGERATION  M7 

At  very  low  temperatures  the  ice  crystals  are  formed  so  rapidly 
that  they  do  not  have  time  to  solidify  so  that  the  block  is  rather 
porous,  being  made  up  of  the  separate  crystals.  With  a  freezing 
temperature  of  15°,  the  tank  for  holding  the  cans  should  be  large 
enough  to  contain  from  2  to  2^  times  the  number  of  cans  necessary  to 
make  up  the  daily  output.  Thus  what  is  called  a  15-ton  tank  will 
really  contain  cans  sufficient  to  hold  about  38  tons  of  ice.  This  factor 
by  which  the  number  of  the  cans  in  the  tank  is  increased  is  known 
as  the  tank  surface.  The  time  of  freezing  depends,  of  course,  on 
the  thickness  of  the  ice,  as  the  first  inch  of  thickness  is  formed  much 
quicker  than  the  rest  of  the  block.  Thus,  with  a  temperature  of 
20°,  a  1-inch  thickness  can  be  frozen  in  an  hour  or  less;  while  a  4- 
inch  thickness  will  require  about  10  hours,  the  cooling  being  from 
one  side  only.  For  this  temperature,  the  time  in  hours  required  to 
freeze  can  be  found  approximately  by  adding  1  to  the  inches  of 
thickness,  multiplying  this  sum  by  the  thickness  in  inches,  and  divid- 
ing the  result  by  2.  Thus  to  freeze  ice  8  inches  thick  from  one  side, 
we  have  8  (8  +  1)  -J-  2  =  36  hours.  For  a  temperature  of  15°  the 
results  obtained  by  the  rule  should  be  decreased  by  20  per  cent  for 
all  thicknesses  under  8  inches,  and  by  25  per  cent  for  thicker  ice. 

Can  Plant  Equipment.  The  complete  can  ice  plant  is  made  up 
of  a  steam  boiler  plant,  a  refrigerating  or  ice-making  machine,  dis- 
tilled water  system,  and  freezing  tank  with  accessories.  In  addition 
to  this  equipment,  it  is  customary  to  provide  ice  storage  rooms  and 
the  necessary  brine  cooling  and  circulating  apparatus.  Pumping 
apparatus  is  also  required  to  supply  water  to  the  plant,  and  in  cases 
where  water  is  scarce  or  obtained  at  great  expense,  cooling  towers 
are  employed.  The  steam  boiler  plant  will  not  be  described  in  de- 
tail as  it  should  differ  in  no  way  from  a  first  class  steam  power- 
plant  equipment.  It  consists  of  a  good  boiler  with  fixtures  and 
stack,  a  boiler  feed  pump,  an  injector,  and  a  feed-water  heater  to- 
gether with  water  softening  or  purifying  apparatus  in  case  the 
water  is^bad.  For  small  plants,  ordinary  return  tubular  boilers 
are  about  the  most  practical  type  and  should  be  installed  so  as  to 
have  a  reserve  unit  if  possible,  particularly  if  the  water  is  bad. 
Larger  plants  may  use  the  more  expensive  water-tube  boilers  to 
advantage  but  there  is  little  need  of  these  except  where  con- 
densing or  compound  engines  are  employed  as  in  plate  plants. 


148 


REFRIGERATION 


The  engines  are  of  standard  manufacture  and  in  no-wise  specially 
constructed  for  the  ice  plant.  The  refrigerating  machine  has  already 
been  discussed  in  detail  so  that  it  only  remains  to  describe  the  dis- 
tilling and  freezing  apparatus  and  show  how  all  the  apparatus  is 
assembled  to  form  the  complete  ice  plant. 

Distilling  Apparatus.  This  consists  of  an  oil  separator,  a  back 
pressure  or  relief  valve,  an  exhaust  steam  condenser,  a  reboiler  and 
skimmer,  a  hot  filter,  a  cooling  coil,  a  gas  forecooler,  and  a  cold  filter. 
Fig.  59  shows  the  course  of  the  steam  from  the  engine  through  ttae 
various  parts  of  the  apparatus.  From  the  engine  cylinder  A,  the 
steam  passes  directly  to  the  oil  separator,  or,  if  a  receiver  is  used,  to 
the  receiver,  and  then  to  the  separator.  The  separator  should  be  of 


Fig.  59.    Diagram  of  Distilled- Water  Apparatus. 

ample  size  and  never  less  than  the  size  of  the  pipe  to  which  it  is  con- 
nected. In  the  separator  the  oil  and  priming  water  that  may  have 
come  over  are  separated  out  and  the  purified  steam  carried  to  the 
exhaust  steam  condenser  B.  Any  steam  that  is  not  condensed  im- 
mediately escapes  through  the  relief  valve  C\  and  the  vent  cock 
D  serves  to  rid  the  steam  of  any  air  and  other  gases  that  may 
be  present.  Water  from  the  steam  condenser  passes  to  the  reboiler 

E,  which   is   provided  with  a    skimming  diaphragm   near  one  end 
over  which  scum  and  light  impurities  can  pass  off  to  the  waste  pipe 

F.  A  float  valve  regulates  the  water  level  in  the  reboiler  and  a  live 
steam  coil  furnishes  the  heat  for  boiling.     After  the  water  is  boiled. 


REFRIGERATION  149 

it  passes  through  the  pipe  G  to  the  hot  filter  H,  and  thence  to  the 
cooling  coil  /  over  which  cooling  water  runs.  From  the  cooling  coil 
the  water  passes  to  the  tank  J  which  contains  a  coil  of  pipe  con- 
nected at  its  two  ends  into  the  suction  line  of  the  compressor.  Thus 
the  return  gas  from  the  expansion  coils  passes  through  the  coil,  and 
the  water  in  the  tank,  which  is  known  as  the  forecooler,  is  cooled 
down  to  a  temperature  of  45°  to  50°.  From  the  forecooler,  the  water 
goes  through  the  cold  filter  and  thence  passes  through  a  hose  to  the 
can  filter  and  thence  to  the  cans. 

Steam  Condenser.  This  usually  consists  of  pipe  coils  over  which 
water  is  run  as  in  the  atmospheric  type  of  ammonia  condenser. 
Either  IJ-inch  or  2-inch  pipe  may  be  used,  care  being  taken  to  have 
sufficient  coils  to  give  a  condensing  area  equivalent  to  about  twice 
the  area  of  the  exhaust  pipe.  This  will  be  found  satisfactory  where 
the  oil  separator  is  of  such  design  as  to  act  as  a  receiver,  or  where  a 
receiver  is  connected  in  the  exhaust  pipe.  The  idea  is  to  avoid 
throwing  back  pressure  on  the  engine,  and  if  the  exhaust  pipe  is  long 
or  has  a  number  of  unavoidable  bends,  the  aggregate  area  of  the 
condenser  pipe  coils  must  be  made  larger  in  proportion.  About 
80  square  feet  of  pipe  surface  should  be  allowed  for  each  ton  of  ice 
making  capacity  in  24  hours.  This  means  128  running  feet  of  2-inch 
or  180  running  feet  of  1  j-inch  pipe  per  ton  of  capacity.  Many  plants 
do  not  use  this  amount  of  pipe,  and  in  cases  where  the  cooling  water 
has  a  low  temperature  the  use  of  less  pipe  surface  may  be  justifiable. 

In  addition  to  the  pipe  coil  condenser,  there  are  a  number  of 
special  designs  on  the  market,  most  of  them  designed  to  economize 
space.  These  generally  consist  of  some  form  of  receiving  tank  made 
of  galvanized  iron,  water  being  run  over  the  outer  surfaces  of  the 
tank.  It  is  claimed  that  the  thin  metal  gives  rapid  and  economical 
transfer  of  heat  and  that  the  cooling  water  is  used  to  the  best  advan- 
tage so  that  less  of  it  is  required.  A  steam  condenser  of  this  type 
made  by  the  Triumph  Ice  Machine  Co.  is  shown  in  Fig.  60.  In 
some  cases  local  conditions  make  it  desirable  to  use  the  regular 
standard  surface  condensers,  this  being  particularly  the  case  where 
the  ice  plant  is  operated  in  combination  with  a  power  plant. 

Hot  Skimmer  and  Reboiler.  Cleansing  of  the  water  formed  by 
condensing  the  steam  is  done  by  driving  off  all  volatile  matter,  dur- 
ing the  process  of  boiling,  and  skimming  such  of  the  impurities  as 


150 


REFRIGERATION 


REFRIGERATION  151 

cannot  be  volatilized.  These  processes  may  be  carried  on  in  two 
separate  pieces  of  apparatus  or  the  hot  skimmer  and  reboiler  may  be 
combined  as  shown  in  Figs.  59  and  61.  The  combined  apparatus 
requires  fewer  pipe  connections  and  is  somewhat  more  simple  and  in- 
expensive. As  seen  in  Fig.  61,  the  skimming  is  accomplished  by  a 
heavy  galvanized-iron  diaphragm  near  one  end  of  the  rectangular 
tank  containing  the  water  to  be  boiled.  The  impurities  and  refuse 
water  flow  over  this  diaphragm  and  out  through  the  pipe  connection 
made  to  the  end  of  the  tank.  Distilled  water  is  brought  to  the  tank 
by  the  connections  A,  the  pipe  being  extended  into  the  tank  and  per- 
forated so  that  the  water  escaping  through  the  holes  is  evenly  difr 


A 

Fig.  61.    Keboiler  and  Skimmer. 

fused  and,  rising  to   the  surface  level  of  the  water  in  the  tank,  gets 
rid  of  any  entrained  air. 

Live  steam  is  supplied  to  the  zigzag  coil  in  the  bottom  of  the 
tank  by  means  of  the  connection  B,  and  being  condensed  in  its  pas- 
sage through  the  cpil  is  allowed  to  escape  through  the  perforations 
shown  at  C  in  the  last  turn  of  the  coil.  It  will  be  seen  from  this  that 
all  water  enters  the  tank  at  the  end  nearest  the  skimming  diaphragm 
and  must  pass  to  the  other  end  of  the  tank  before  going  through  the 
outlet  valve  D  to  the  hot  filter.  During  this  passage  the  water  is 
thoroughly  boiled  by  the  heat  from  the  live  steam  coil  and  is  freed 
from  any  impurities  and  air  it  may  have  contained.  The  outlet 
valve  is  controlled  by  a  float  and  is  so  constructed  that  it  is  wide  open 
while  the  tank  is  full  and  closes  gradually  as  the  water  level  falls  until, 
when  the  level  is  about  3  inches  above  the  outlet,  the  valve  is  entirely 
closed.  Thus  there  is  no  chance  for  air  to  be  drawn  off  with  the  water 


152  REFRIGERATION 

as  would  be  the  case  if  the  valve  remained  open  until  the  water  level 
should  fall  as  low  as  the  outlet  opening. 

Filters.  Filters  usually  consist  of  vertical  cylindrical  tanks 
made  of  heavy  sheet  iron  or  cast  iron  with  the  interior  surfaces  well 
galvanized.  A  perforated  false  bottom  supports  the  filtering  ma- 
terial in  place,  crushed  quartz,  sand,  or  good  charcoal  being  used  for 
this  purpose.  Quartz  is  preferable  for  the  hot  filter  but  charcoal 
is  frequently  used  for  this  as  well  as  for  the  cold  filter.  All  pipe  con- 
nections are  made  to  the  side  of  the  tank  so  that  the  covers  can  be 
removed  for  cleaning  and  recharging  and,  in  addition  to  stop  cocks 
and  valves  on  the  pipe  connections,  a  by-pass  with  proper  valves 
should  be  provided  so  that  cleaning  can  be  done  without  interfering 
with  the  operation  of  the  plant.  The  frequency  with  which  the 
filtering  material  must  be  renewed  depends  altogether  on  local  con- 
ditions, and  varies  from  every  week  or  ten  days  to  once  a  season. 
Under  average  conditions  renewal  once  a  season  or,  at  most,  twice 
will  be  found  satisfactory. 

The  water  may  run  through  the  filter  from  the  top  down,  as  is 
usually  done,  or  the  direction  of  flow  may  be  reversed  according  to 
the  preferences  of  the  engineer  in  charge.  In  the  average  filter,  the 
depth  of  the  filtering  material  is  about  5  feet.  The  surface  area 
required  depends  on  local  conditions.  Filters  are  ordinarily  from 
30  to  40  inches  in  diameter  and  one  hot  filter  of  this  size,  7  feet  high 
over  all,  is  about  right  for  a  15-ton  plant.  For  the  cold  filter,  1 
square  foot  of  surface  will  suffice  for  a  plant  of  the  same  size.  In 
small  plants  the  cold  filter  is  often  a  very  small  affair  known  as  a 
sponge  filter  and  may  consist  of  nothing  more  than  a  sheet-metal 
cylinder  about  20  inches  long  and  8  or  10  inches  in  diameter  with 
proper  connections  at  its  two  ends  for  the  water  pipes.  Charcoal, 
grass  sponges,  or  other  filtering  material  is  placed  in  one  end  and  the 
other  end  is  filled  with  alternate  layers  of  cotton  and  cloth  of  fine 
weave.  This  arrangement  is  considered  very  effective  in  catching 
rust  and  other  material  that  gives  red  core  ice. 

Cooling  Coils  and  Gas  Cooler.  After  leaving  the  hot  filter,  the 
distilled  water  goes  to  the  cooling  coils  constituting  the  fiat  cooler,  in 
the  manner  already  described.  These  coils  are  built  like  the  steam 
condenser  but  are  usually  of  a  smaller  sized  pipe.  In  fact  the  coils 
are  nothing  more  than  an  atmospheric  condenser  used  to  cool  water 


REFRIGERATION 


153 


instead  of  to  condense  steam.  About  4  square  feet  of  pipe  surface 
should  be  allowed  for  each  ton  of  ice-making  capacity.  As  the  cool- 
ing coils  may  be  compared  to  the  atmospheric  condenser,  so  also 
the  gas  forecooler  may  be  likened  to  the  submerged  condenser.  In 
the  case  of  the  forecooler,  however,  the  cooling  medium — expanded 
gas — flows  through  the  coils  and  the  water  to  be  cooled  fills  the  tank, 
whereas  with  the  condenser  the  water  filling  the  tank  does  the  cool- 
ing and  the  gas  inside  of  the  pipe  coil  is  condensed. 

For  small  plants  the  tank  for  the  forecooler  should  preferably 
be  cylindrical  and  the 
pipe  coil  be  made  in  the 
form  of  a  spiral  without 
joints.  Such  a  cooler  is 
illustrated  in  Fig.  62, 
showing  the  Triumph 
construction.  Larger 
plants  have  the  cylin- 
drical or  rectangular  tank 
as  best  suits  local  con- 
ditions. The  combined 
area  of  the  coils  in  every 
case  should  not  be  less 
than  the  area  of  the  suc- 
tion pipe  of  the  com- 
pressor and  should  pre- 
ferably be  from  1|  to  2 
times  greater.  This  pro- 
portion will  ordinarily 
give  from  4  to  5  square 
feet  of  cooling  surface 

per  ton  of  ice,  which  is  about  right  for  average  conditions.  Care 
should  be  taken  to  see  that  all  the  connections  of  the  distilled  water 
apparatus  are  of  block  tin  or  galvanized  iron  so  that  no  trouble  will  be 
had  with  rust.  The  reboiler  and  other  vessels  should  be  made  of  gal- 
vanized iron  or  have  the  surfaces  in  contact  with  the  water  thoroughly 
galvanized.  Valves  should  be  of  composition.  Connections  should  be 
made  to  blow  out  all  parts  of  the  system  with  live  steam  as  occasion  may 
require,  andblow-off  cocks  should  be  provided  at  convenient  points. 


Fig.  62.    Distilled  Water  Storage  Tank. 


154 


REFRIGERATION 


Freezing  Tank.  The  freezing  tank  with  its  accessory  apparatus 
is  the  center  of  operations  in  the  ice  plant.  The  complete  equipment 
includes  ice  cans,  with  covers  to  be  placed  over  them  in  the  spaces 
of  the  floor  grating  that  holds  them  in  position;  a  brine  agitator;  a 
crane  with  geared  hoist  and  can  lift;  an  ice  can  dump  with  thawing 
apparatus;  a  can  filler  with  hose  to  reach  any  part  of  the  tank  room 
floor;  expansion  coils  with  headers  and  valves;  a  brine  hydrometer 
and  a  thermometer.  The  tank  itself  is  made  of  metal  or  wood  and 
should  be  well  insulated,  one  method  of  doing  which  has  been  de- 


Fig.  63.    Construction  of  Tank  Grating  and  Covers. 

scribed  in  discussing  brine  cooling  tanks.  For  tanks  up  to  30  inches 
deep,  fV-inch  steel  is  thick  enough,  but  for  deeper  tanks  up  to  about 
4  feet  the  thickness  should  be  |-inch.  The  sides  and  ends  should 
be  well  braced  with  angle  irons  and  an  angle-iron  rim  should  be  put 
around  the  top.  Sufficient  holes  should  be  punched  in  this  rim  to 
make  sure  that  the  grating  can  be  bolted  securely  in  position. 

Expansion  Coils.  The  expansion  coils  should  be  of  extra 
heavy  welded  pipe  running  the  full  length  of  the  tank  if  possible  and 
held  in  position,  a  coil  between  each  two  rows  of  cans,  by  iron  straps. 
These  straps  also  support  the  grating,  as  seen  in  Fig.  63.  The  inlet 
of  each  coil  is  fitted  with  an  expansion  valve  and  each  of  the  outlets  is 
provided  with  a  stop  valve.  Thus  any  coil  may  be  cut  out  of  opera- 
tion, if  it  is  found  to  be  leaking,  without  interfering  with  the  operation 
of  the  plant.  All  of  the  coils  of  the  tank  are  connected  to  a  manifold 
at  the  inlet  end,  the  connection  being  made  so  that  the  expansion 


REFRIGERATION  155 

valve  is  between  the  coil  and  the  manifold.  A  similar  manifold  is 
used  to  connect  the  outlets  of  all  the  coils  with  the  suction  of  the  com- 
pressor. Ordinarily  the  bottom  jeed  is  used,  the  liquid  ammonia 
entering  the  bottom  pipe  of  each  coil  and  passing  off  to  the  suction 
manifold  from  the  upper  pipe  of  the  coil;  but  this  method  of  feeding 
is  reversed  where  the  wet  system  of  operation  is  used.  Thus  there 
are  two  methods  of  feeding  the  coils,  each  of  which  has  its  advan- 
tages and  disadvantages. 

There  is  also  a  third  system  of  operation  known  as  the  top  jeed 
and  bottom  expansion  which  is  a  combination  of  the  two  methods  just 
described.  At  the  feeding  end  of  the  coils  a  manifold  is  connected 
to  each  alternate  coil  and  the  ammonia  is  fed  downward  in  these 
coils  as  in  the  wet  system.  The  bottom  ends  of  all  the  coils  are  con- 
nected to  a  common  manifold  so  that  the  liquid  after  flowing  down 
through  half  of  the  coils,  rises  and  evaporates  through  the  other  coils 
and  finally  passes  to  a  third  or  suction  manifold  which  is  connected 
to  the  upper  ends  of  the  coils  not  connected  to  the  feeding  manifold. 
The  gas  passes  from  this  third  manifold  to  the  suction  of  the  com- 
pressor. There  should  be  220  lineal  feet  of  2-inch  pipe  or  350  feet 
of  l|-inch  pipe  for  each  ton  of  ice  to  be  made  in  24  hours,  due  regard 
being  had  for  the  temperature  of  the  brine  and  the  most  economical 
capacity  of  the  machine.  It  is  true  that  many  tanks  are  installed 
with  much  less  pipe  surface  than  this,  but  the  plants  so  installed  are 
necessarily  operated  extravagantly,  as  the  back  pressure  must  be 
carried  very  low  to  get  capacity.  This  low  pressure  calls  for  more 
coal,  and  is  the  cause  of  increased  depreciation  of  the  apparatus. 

Ice  Cans.  Ice  cans  are  made  in  50-,  100-,  200-,  300-,  and  400- 
pound  standard  sizes,  the  top  and  bottom  dimensions  for  each  of  the 
sizes  respectively  being  8x8  and  1\  x  7$  inches,  8x16  and  1\  x  15 \ 
inches,  11^x22$  and  10$  x 20$  inches,  Il$x22$  and  10£  x  21$ 
inches,  and  11$  x22$  and  10$  x  21$  inches.  For  the  50-  and  100- 
pound  can,  the  inside  and  outside  depths  are  respectively  31  and  32 
inches,  while  for  the  200-  and  300-pound  cans  the  depths  are  44  and 
45  inches,  and  the  400-pound  can  has  an  inside  depth  of  57  inches 
with  an  outside  depth  of  58  inches.  Reinforcing  rings  are  used 
around  the  tops  of  the  cans  which  are  made  of  iron  bands  f-inch 
thick  by  1$  inches  wide.  All  except  the  400-pound  cans  are  made  of 
No.  16  steel,  U.  S.  gauge,  and  these  cans  are  made  of  No.  14  material. 


15C  REFRIGERATION 

The  metal  should  be  of  good  quality  and  of  uniform  thickness  and 
all  except  the  largest  cans  should  be  made  with  but  one  side  joint. 
All  joints  are  riveted  on  1-inch  centers,  the  rivets  being  driven  close 
and  the  seams  soaked  with  solder  and  floated  flush.  The  bottoms 
are  flanged  and  inverted  1  inch  into  the  body  of  the  can.  All  bands 
are  welded  and  galvanized  and  should  be  punched  in  the  middle  of 
the  long  sides  with  f-inch  holes  placed  1 TV  inches  from  the  top  of 
the  band.  Cans  made  of  No.  16  steel  should  have  the  sides  turned 
over  at  the  top  and  bottom. 

Grating  and  Covers.  Gratings  and  covers  for  holding  the  ice 
cans  in  position  are  constructed  as  shown  in  Fig.  63.  The  rim  of 
the  can  rests  on  a  galvanized-iron  cross-strap  A  which  is  mortised 
into  the  oak  strip  B.  Above  and  below  the  strip  B  are  strips  C  and 
G,  and  all  three  of  the  strips  are  held  together  by  through  bolts,  as 
shown  in  the  illustration.  The  whole  structure  is  supported  on  the 
iron  straps  that  hold  the  expansion  coils  in  position,  these  traps  being 
mortised  into  the  strip  G  as  shown.  Grooves  E  are  cut  into  the  sides 
of  the  strip  C  and  a  stick  F,  having  its  ends  set  in  these  grooves,  serves 
to  hold  the  cans  down  so  that  they  cannot  float.  The  covers  D  rest 
on  the  strips  C  and  in  common  with  the  other  parts  of  the  grating  are 
made  of  oak,  two  thicknesses  being  used  with  good  insulating  paper 
between  them.  These  boards  must  be  thoroughly  nailed  together, 
as  they  are  subjected  to  rather  severe  usage  and  have  a  tendency  to 
warp  out  of  shape.  Some  means  should  be  provided  for  lifting  them 
and  this  may  be  done  by  hollowing  out  hand  holes  at  the  ends  or  by 
providing  regular  plates  and  handles. 

Brine  Agitators.  Brine  agitators  are  of  three  classes,  using 
centrifugal  pumps,  displacement  pumps,  and  propellers  respectively. 
As  the  object  in  all  cases  is  to  get  a  steady,  uniform  circulation 
of  the  brine  in  all  parts  of  the  tank,  it  is  plain  that  the  propeller  is 
well  adapted  to  the  work  and  for  this  reason  it  is  used  in  the  great 
majority  of  cases.  Where  brine  coils  are  placed  in  the  ice  storage 
house  or  where  coolers  are  operated  in  connection  with  the  ice  plant, 
there  is  an  advantage  in  using  a  displacement  pump,  as  the  brine 
when  drawn  from  the  tank  may  be  pumped  through  the  cooling  coils 
before  being  returned.  When  this  method  of  circulating  the  brine 
is  adopted,  discharge  pipes  must  be  put  in  the  tank  so  that  the  return- 
ing brine  will  be  distributed  throughout  the  entire  tank.  One  of  these 


REFRIGERATION 


157 


pipes  is  placed  under  each  of  the  expansion  coils  and  small  holes  in 
the  pipes  distribute  the  brine  all  along  the  coils.  In  this  way  a  cur- 
rent is  set  up  at  each  of  the  coils  and  the  comparatively  warm  brine 
returned  by  the  pump  from  the  cooler  coils  is  brought  in  direct  con- 
tact with  the  expansion  coils,  with  a  resulting  high  efficiency  of  heat 
absorption  by  the  expanding  gas. 

In  the  use  of  the  centrifugal  pump,  the  chief  point  of  advan- 
tage lies  in  the  fact  that  a  large  quantity  of  brine  can  be  circulated. 
The  brine  is  taken  from  one  corner  of  the  tank  and  discharged  into 
a  header  on  the  side  of  the  tank  opposite  the  suction  connection  of 
the  pump.  The  rapid  circulation  set  up  in  this  way  causes  rapid 
freezing  which  is  a  great  advantage  when  ice  is  needed  in  increased 
quantities  to  meet  the  demands  of  the  market  in  hot  weather. 


Fig.  64.    Construction  of  Freezing  Tank. 

Where  a  propeller  is  used  for  circulating  the  brine,  as  shown  in 
Fig.  64,  which  is  a  longitudinal  section  through  a  freezing  tank, 
one  or  more  wooden  partitions  are  constructed  in  the  brine  tank  be- 
tween the  cans  and  along  the  expansion  coils  for  almost  their  entire 
length.  The  propeller  is  driven  by  a  direct-connected  engine  or  by 
a  motor,  and  forces  the  brine  to  circulate  by  moving  from  the  dis- 
charge side  through  the  length  of  one  compartment,  around  the  end 
of  the  wooden  partition  and  back  through  the  other  compartment 
to  the  suction  side  of  the  propeller.  Thus  it  is  seen  that  there  are 
two  passages  essential  to  the  operation  of  the  system,  one  of  the  pas- 
sages being  open  to  the  suction  and  the  other  to  the  discharge  side  of 
the  propeller.  Where  only  one  propeller  is  used  on  a  tank,  it  is 
advisable  to  use  two  partitions  so  that  the  suction  passage  of  the 


158  REFRIGERATION 

propeller  is  divided  into  two  parts.  The  propeller  is  placed  near  the 
center  of  the  tank  at  one  end  and  discharges  through  the  middle  com- 
partment between  the  two  partitions,  and  the  brine,  arriving  at  the 
far  end  of  the  tank,  is  divided  into  two  streams  that  flow  back  by  the 
side  passages  outside  of  the  partitions  to  the  suction  of  the  propeller. 
For  a  10-ton  tank,  a  12-inch  propeller  of  ample  size,  and  for  a  15- 
ton  tank  an  18-inch  propeller  should  be  used.  Larger  tanks  re- 
quire more  than  one  propeller.  In  planning  a  method  for  circula- 
ting the  brine,  one  should  remember  that  a  comparatively  large 
amount  of  power  is  required  to  operate  the  propeller  system. 

Crane  and  Hoist.  The  great  majority  of  small. and  medium 
sized  plants  use  hand  cranes,  consisting  of  a  light  channel  iron  car- 
ried on  four  wheels,  which  run  on  suitable  rails  placed  at  a  con- 
venient height  on  the  side  walls  of  the  tank  room.  The  channel 
iron  carries  a  four-wheeled  trolley  provided  with  a  geared  hoist  on 
the  drum  of  which  is  wound  the  hoisting  chain  or  rope.  A  can 
latch,  one  form  of  which  is  shown  in  Fig.  65,  is  attached  to  the  end 
of  the  chain.  The  apparatus  consists  of  a  board  mortised  out  at 
the  ends  so  as  to  drop  into  the  top  of  the  can.  In  the  middle  is  an 
eyebolt  to  which  the  hoisting  chain  is  connected  and  hook  latches  a* 
the  two  ends  are  adapted  to  catch  in  the  holes  in  the  sides  of  the  can. 
When  the  can  has  been  lifted  and  is  to  be  set  down  on  the  dumping 
table  the  latches  are  pulled  outward  so  as  to  release  the  hooks.  With 
the  hand  crane  and  an  apparatus  of  this  kind,  a  man  can  handle 
about  15  tons  of  ice  in  a  day  of  12  hours.  For  plants  of  larger  capacity 
it  is  advisable  to  use  a  pneumatic  hoist  and  when  this  is  done  a  special 
latch  may  be  used  so  that  two  or  more  cans  may  be  lifted  at  the  same 
time.  With  this  kind  of  hoist,  one  man  can  handle  from  40  to  50 
tons  of  ice  in  12  hours.  In  still  larger  plants,  special  means  are  used 
to  hoist  the  cans  and  dump  the  ice. 

Dumping  and  Filling.  The  dumping  and  filling  of  the  cans 
should  be  done  according  to  some  regular,  well-ordered  system 
of  rotation.  Numbers  should  be  plainly  stenciled  or  cut  on  the 
covers  of  the  cans  so  that  the  tankmen  need  make  no  mistake  in 
pulling  the  proper  cans.  All  the  cans  should  not  be  pulled  from  any 
one  part  of  the  tank  at  the  same  time,  and  except  in  large  tanks  it  is 
not  well  to  take  all  the  cans  of  any  one  row  at  a  single  pull.  As  an 
example  of  what  may  be  done,  suppose  that  the  cans  are  numbered 


REFRIGERATION 


159 


in  consecutive  order  over  the  entire  tank.  The  tankman  could  then 
pull  every  fourth  can,  taking  the  numbers  1,  5,  9,  etc.  At  the  next 
pull  he  would  take  the  numbers  2,  6,  10,  etc. 

Various  styles  of  dumping  tables  are  in  use,  varying  from  a 
simple  home-made  apparatus  designed  to  handle  one  oan  at  a  time, 
to  the  elaborate  apparatus  of  a  large  plant  dumping  a  number  of  cans 
at  one  operation.  The  can  may  be  dipped  into  a  hot-water  tank  to 
thaw  the  ice  block  loose,  or  tepid  water  may  be  sprinkled  over  it  to 
accomplish  the  same  purpose,  as  is  done  with  the  style  of  apparatus 
illustrated  in  Fig.  66. 


n 


n 


Fig.  65.    Can  Latch. 


\ 

Fig.  66.    Automatic  Can  Dump. 


The  table  here  shown  is  constructed  of  metal  and  consists  of  a 
drip  pan  A  on  the  bottom  of  which  are  riveted  two  pairs"  of  support- 
ing brackets  B,  made  of  pipe.  Hollow  trunnions  C  are  connected 
to  the  water  supply  and  sprinkler  pipes  and  support  the  box  D, 
in  which  the  can  is  placed.  The  ports  in  the  hollow  trunnion  are 
so  arranged  that  when  the  box  is  in  the  position  shown  by  the  full 
lines,  the  water  connection  is  shut  off.  However,  as  soon  as  the  box 
is  tilted  to  the  dumping  position  shown  by  the  dotted  lines,  the  con- 
nection to  the  water  supply  is  made  and  water  flows  over  the  can 
from  the  sprinkler  pipes  until  the  block  of  ice  is  thawed  out. 
When  this  occurs,  the  weight  of  the  can,  which  is  not  evenly  bal- 
anced on  the  trunnions,  acts  to  return  the  box  to  the  first  position, 
in  doing  which  the  water  is  shut  off.  Thus  the  operation  is  auto- 


160 


REFRIGERATION 


matic  and  the  tankman,  having  placed  a  can  in  the  tilting  position, 
gives  it  no  further  attention  until  he  pulls  and  brings  up  another  can 
to  be  put  in  the  place  of  that  from  which  the  ice  has  been  dumped. 
The  empty  can  is  then  returned  to  its  place  in  the  tank  and  filled 
with  distilled  water  from  the  supply  hose  by  means  of  an  automatic 
can  filler  which  is  placed  in  the  can  and  the  trigger  pulled, 
after  which  the  attendant  leaves  it  and  goes  about  his  business. 
When  the  water  rises  to  the  desired  level,  it  raises  a  float  that 
automatically  moves  the  trigger  to  shut  off  the  water  supply.  By 
using  this  apparatus  all  cans  are  filled  to  the  same  level  without 
special  attention. 

Layout.     The  layout  of  a  plant  should  be  given  the  most  care- 
ful consideration  as  success  or  failure  depends  to  a  large  extent  on 


Fig.  67.    Layout  of  Wolf  Plant. 


the  arrangement  of  the  different  parts  with  reference  to  convenience 
and  economy  in  operation.  No  set  designs  can  be  given  which  will 
meet  the  local  conditions  of  every  case,  but  plans  of  a  few  typical 
plants  are  given  to  show  what  should  be  sought  for  in  constructing 
a  plan  suitable  for  any  particular  case.  Where  local  conditions  do 
not  require  specially  constructed  buildings,  the  whole  plant  may  be 
housed  in  a  single  building  of  rectangular  form  such  as  that  shown  in 
Fig.  67.  This  design  is  by  the  Fred  W.  Wolf  Co.  and  has  been  used 
as  a  basis  of  work  in  designing  a  large  number  of  successful  plants. 
The  boilers  are  in  the  end  of  the  building  remote  from  the  freezing 


REFRIGERATION 


161 


tank,  and  the  ice  machine  is  so  set  that  as  little  as  possible  of  the  heat 
radiated  from  steam  pipes,  etc.,  will  get  to  the  tank  room.  The 
overall  dimensions  for  a  plant  of  this  kind  are  given  in  Table  19  for 
capacities  ranging  from  5  to  100  tons.  Fig.  68  shows  a  diagram  plan 
and  elevation  of  a  design  used  by  the  Arctic  Ice  Machine  Co.  The 
dimension  letters  refer  to  Table  20  which  gives  a  complete  schedule 
of  dimensions  for  plants  ranging  in  capacity  from  2  to  200  tons  daily 
output.  All  dimensions  given  in  the  table  are  in  feet. 

TABLE  XIX 
Dimensions  for  Fig.  67 


DAILY  CAPACITY 

DIMENSIONS 
A                    B 

5  tons 

30  feet 

56  feet 

10 

35 

73  " 

15 

37 

78 

20 

40 

85 

25 

42 

95 

30 

" 

42 

107 

35 

42 

117 

40 

49 

120 

50 

49 

135 

60 

54 

150 

80 

59 

154 

100 

73 

160 

Fig.  69  shows  another  arrangement  for  a  small  factory.  This 
is  a  design  of  the  Frick  Co.  and  is  suitable  for  a  plant  having  a  daily 
output  of  from  6  to  10  tons.  For  a  plant  of  about  35  tons  capacity, 
the  Frick  Co.  uses  the  design  shown  in  Fig.  70,  which  gives  sec- 
tional side  and  end  elevations  and  a  plan  view.  Another  design  by 
the  same  company  for  a  ICO-ton  plant  is  shown  in  Fig.  71.  These 
three  illustrations  give  an  idea  of  the  necessary  changes  in  arrange- 
ment for  plants  of  different  sizes.  Fig.  72  shows  in  plan  and  elevation 
a  modern  ice  factory  as  constructed  by  the  Triumph  Ice  Machine  Co. 

Where  absorption  machinery  is  used,  the  arrangement  of  ma- 
chinery may  be  modified  if  desired  so  as  to  make  the  plant  somewhat 
more  compact,  for  the  same  capacity,  than  a  plant  operating  with 
compression  machinery.  This  ability  to  compact  the  arrangement 
is  due  principally  to  the  fact  that  in  the  absorption  machine  there  are 
no  moving  parts,  the  only  moving  machinery  being  the  pumps.  A 
good  plan  for  an  absorption  plant  is  that  used  by  the  Henry  Vogt 
Machine  Co.,  an  isometric  view  of  which  is  shown  in  Fig.  73. 


162 


REFRIGERATION 


Plate  System.  Although  plate  ice  may  be  produced  by  freez- 
ing from  two  sides  of  the  compartment  containing  the  water  and 
allowing  the  ice  cakes  to  meet,  thereby  reducing  the  time  of  freezing, 
this  has  not  been  done  to  any  extent.  Practically  all  plate  ice  is 
frozen  from  one  side  only  and  on  this  account  a  great  deal  of  time  is 


ienses 
Weight  /oolbs 
pertf  "•  * 


N 


^Better  Room 
M 


JE'/ipt/ie       Q 
ftoom 


Ammonia  Condenser 
-  Weiyht 


/ce  Tank  Room 


Fig.  68.    Arrangement  of  Arctic  Plant. 

required,  about  eight  or  ten  days  being  necessary  to  freeze  11 -inch 
ice.  The  time  of  freezing  for  a  20-degree  temperature  is  determined 
by  a  rule  similar  to  that  given  for  the  can  system,  viz :  Multiply  the 
thickness  to  be  frozen  by  twice  itself  plus  one.  For  a  temperature 
of  15°,  deduct  one-fourth  from  the  result  thus  found.  Thus  for 
11-inch  ice  we  have  11  (2x11  +  1)=  253  hours  and  deducting  one- 
fourth  the  freezing  time  at  15°,  is  about  190  hours.  The  freezing 


REFRIGERATION 


163 


TABLE  XX 
Dimensions  for  Fig.  68 


CAPACITY  n 
TONS  ICE 

A 

B 

c 

D 

E 

p 

G 

H 

J 

K 

L 

M 

N 

o 

p 

Q 

R 

s 

T 

2 

47 

28 

17 

10 

18 

10 

10 

28 

12 

8 

18 

16 

20 

6 

9 

16 

5 

12 

10 

5 

48 

42 

17 

10 

82 

10 

10 

42 

13 

8 

32 

16 

20 

6 

9 

16 

5 

12 

10 

8 

61 

34 

19 

12 

24 

12 

10 

34 

22 

8 

24 

16 

20 

6 

10 

16 

5 

12 

10 

10 

72 

34 

21 

15 

24 

15 

10 

34 

26 

10 

24 

16 

20 

6 

10 

16 

5 

12 

10 

12 

72 

38 

21 

15 

28 

15 

10 

38 

26 

10 

28 

16 

20 

6 

10 

16 

5 

12 

10 

15 

78 

44 

24 

18 

34 

18 

10 

44 

26 

10 

34 

10 

20 

6 

12 

20 

5 

12 

10 

18 

80 

50 

24 

18 

40 

18 

10 

50 

26 

12 

40 

16 

20 

6 

12 

20 

5 

12 

10 

20 

87 

46 

25 

18 

36 

18 

10 

46 

32 

12 

36 

16 

22 

6 

12 

20 

5 

12 

10 

25 

89 

54 

25 

20 

44 

20 

10 

54 

32 

12 

44 

16 

22 

6 

12 

20 

5 

12 

10 

30 

92 

62 

25 

20 

50 

20 

12 

02 

32 

15 

52 

16 

22 

6 

12 

20 

5 

12 

10 

35 

93 

70 

26 

20 

68 

20 

12 

70 

32 

15 

60 

16 

22 

6 

12 

22 

5 

12 

10 

40 

93 

79 

26 

20 

67 

20 

12 

79 

32 

15 

6!) 

16 

22 

6 

12 

22 

5 

12 

10 

50 

144 

54 

35 

25 

39 

25 

15 

54 

64 

20 

44 

20 

22 

6 

12 

24 

5 

12 

10 

60 

145 

62 

86 

25 

47 

25 

15 

62 

64 

20 

52 

20 

25 

6 

12 

24 

5 

12 

10 

75 

160 

79 

46 

80 

64 

30 

15 

79 

64 

20 

69 

20 

25 

6 

12 

27 

5 

12 

10 

100 

173 

59 

54 

80 

80 

30 

15 

95 

64 

25 

85 

20 

25 

6 

12 

30 

5 

12 

10 

150 

247 

95 

76 

40 

80 

30 

15 

95 

96 

35 

85 

20 

25 

6 

12 

30 

5 

12 

10 

200 

333 

95 

100 

40 

SO 

30 

15 

1)5 

128 

45 

85 

20 

25 

6 

12 

30 

5 

12 

10 

THROU6H  D/JT/LL/nG  ROOM 

Fig.  69.    Prick  10-Ton  Plant. 


Fig.  70.    Frick  35-Ton  Plant. 


166 


REFRIGERATION 


apparatus  of  the  plate  plant  consists  of  a  tank  divided  into  compart- 
ments and  fitted  with  freezing  plates;  a  forecooling  tank  with  coils; 
a  crane  and  hoists;  a  tilting  table;  cutting-up  saws;  water  filters  and 
pipe  connections  for  supplying  water. 


Mac 


•5/OE.  JLLLVATION 


dffl 


ffeezi'ncf      Tank      fee. 


Pt.An 


Fig.  71.    Frick  100-Ton  Plant. 

There  are  two  methods  of  operation.  The  first  method,  which  is 
known  as  the  dry-plate  system,  is  that  in  which  ammonia  gas  is  ex- 
panded directly  in  pipe  coils  that  make  up  the  freezing  plate,  the  spaces 
between  the  pipes  being  filled  in  with  wood  or  other  material  to  form 
a  smooth  freezing  surface  on  the  two  sides  of  the  coil.  In  the  wet- 


168 


REFRIGERATION 


REFRIGERATION 


plate  system,  brine  is  used  and  is  closed  up  in  a  metal  cell  or  tank  from 
4  to  6  inches  thick  and  of  the  size  necessary  to  form  the  freezing  plate. 
This  imprisoned  brine  is  kept  cold  by  ammonia  expanding  in  a  pipe 
coil  placed  in  the  tank.  In  some  cases  the  plate  and  the  attached 
blocks  of  ice  are  removed  from  the  tank  bodily,  by  disconnecting 
the  pipe  connections  to  the  expansion  coil  after  drawing  off  the  am- 
monia in  the  coil.  Where  this  is  done,  provision  is  made  to  drain 
the  cold  brine  into  another  of  the  hollow  plates  which  is  immediately 
placed  in  the  tank  so  that  the  freezing  process  goes  on  while  the 
ice  is  being  detached  from  its  plate  and  disposed  of. 

In  another  form  of  the  wet-plate  system  the  cells  forming  the 
freezing  plates  are  designed  to  have  cold  brine  pumped  in  at  the  top 


Fig.  74.    Coil  Plate  with  Wood  Filling. 

and  run  down  in  a  thin  sheet  over  the  inner  surfaces  of  the  plate  and 
collect  at  the  bottom  of  the  cell,  from  which  it  is  drawn  off  by  the 
brine  circulating  pump.  The  great  difficulty  with  all  applications 
of  the  wet-plate  system  is  that  of  making  the  cells  tight.  It  is  almost 
impossible  to  roll  large  plates  which  will  not  show  up  small  leaks  and 
a  few  such  leaks  turn  enough  brine  into  the  water  to  ruin  the  ice. 
This  difficulty  of  obtaining  tight  plates  stands  in  the  way  of  freezing 
by  expansion  of  ammonia  direct  into  a  cell  on  the  sides  of  which  the 
ice  is  frozen.  The  cells  can  easily  be  made  tight  against  the  es- 
cape of  brine  under  small  difference  of  pressure  but  to  make  them 
tight  enough  to  retain  expanding  ammonia  gas  is  impossible  except  at 


170 


REFRIGERATION 


prohibitive  expense.  In  the  dry-plate  system,  pipe  coils  can  be 
made  to  hold  the  gas  where  care  is  taken  in  welding  the  pipe  and  in 
making  the  joints;  the  chief  difficulty  has  been  that  of  getting  suit- 
able surfaces  against  which  to  freeze  the  ice,  while  using  the  coils. 

In  small  plants  the  ice  is  allowed  to  freeze  directly  to  the  coils 
and  is  then  cut  loose,  but  this  is  wasteful  of  ice  and  of  labor.  Wood 
filling  between  the  pipes  of  the  coils  is  not  stable  enough  to  with- 
stand the  rough  usage  to  which  the  plates  are  subjected,  and  on 

this  account  smooth  metal 
plates  are  bolted  on  each 
side  of  the  coil  and  its 
wood  filling,  as  shown  in 
Fig.  74.  Plates  of  this  kind 
are  placed  in  the  compart- 
ments of  the  freezing  tank 
about  30  inches  apart  on 
centers,  and  the  tank  is 
filled  with  water  to  within 
about  9  inches  of  the  top 
of  the  plate.  As  the  am- 
monia is  expanded  directly 
into  the  coil,  the  cooling  is 
very  rapid  and  on  this  ac- 
count great  care  must  be 
taken  in  feeding  or  the  ice 
will  be  frozen  before  the  air 
and  impurities  have  had 
time  to  be  separated  out. 
Another  difficulty  with  the  dry-plate  system  of  operation  is  the  fact 
that  the  ice  forms  thicker  where  the  ammonia  is  fed  into  the  coil 
than  over  the  rest  of  the  plate  so  that  the  block  is  not  of  uniform 
thickness.  These  difficulties  are  avoided  to  some  extent  by  expand- 
ing the  gas  into  a  forecooler  before  turning  it  into  the  plate  coils, 
but  after  all  the  dry  plate  is  difficult  to  operate  successfully. 

This  difficulty  is  offset,  at  least  partially,  by  the  fact  that  the  dry- 
plate  apparatus  is  comparatively  inexpensive  to  install  while  the  wet- 
plate  system  with  its  brine  storage  tank,  brine  pump,  and  extra  piping 
for  the  brine  is  expensive  to  install  and  somewhat  extravagant  in 


Fig.  75.    Cell  Plate. 


REFRIGERATION 


171 


operation  on  account  of  the  extra  transfer  of  heat  to  the  brine.  Fig. 
75  shows  a  cross  section  of  a  cell  such  as  is  used  with  the  wet- 
plate  system.  The  quantity  of  brine  in  the  cell  acts  as  a  kind  of 
fly-wheel  or  balancer  for  the  system  and  aids  materially  in  regula- 
ting the  temperature  to  the  uniform  standard  required  for  making  good 
ice  with  the  water  available.  Different  waters  require  different  brine 
temperatures,  more  time  being  allowed  where  the  water  is  impure. 
Practice  with  the  given  plant  is  the  only  way  to  determine  the  best 
temperature  for  getting  good  ice  in  a  given  case. 

Slabs  of  ice  frozen  on  the  plate  system  may  weigh  from  1  to  10 
tons,  the  maximum  dimensions  being  about  16  x  9  feet  by  12  inches 


•Jec  £ional  End  View 


•Sectional    -Side  View 
Fig.  76.    Eclipse  Plate  System. 


thick.  In  the  United  States  the  cakes  are  usually  about  14  x  8  feet 
by  11  inches.  During  the  process  of  freezing  the  impurities  elimi- 
nated and  thrown  out  settle  to  the  bottom  and  may  be  washed  out 
before  refilling  the  compartment  with  fresh  water,  if  considered  neces- 
sary. Heavy  traveling  cranes  are  used  to  lift  the  ice  when  frozen 
and  transport  it  to  the  cutting  floor  to  which  it  is  lowered  from  the 
vertical  position  by  the  tilting  table.  Power-driven  gang  saws  are 
now  made  to  cut  the  cakes  up  automatically  into  any  size  blocks 
desired,  and  chain  conveyors  take  the  blocks  from  the  table  to  the 
storage  room  or  loading  platform.  The  whole  process  of  lifting  is 
done  as  readily  as  one  lifts  a  single  can  from  a  tank,  everything  being 
done  by  power.  Fig.  76  shows  a  sectional  elevation  of  a  plate  plant 


REFRIGERATION 


173 


built  on  the  Eclipse  plan  used  by  the  Frick  Co.,  while  Figs.  77  and 
78  show  plan  and  sections  in  outline  for  a  25-ton  plate  plant  as 
designed  by  the  Vilter  Mfg.  Co.,  for  electric-motor  drive.  The 


tfacuyft  fonn  ROOM  ancCLne/ 
Fig.  78.    Front  and  Side  Views  of  Vilter  Plate  Plant. 

drawings,  it  will  be  noted,  show  complete  details  and  dimensions, 
while  the  notes  are  self-explanatory.  There  is  only  one  bulkhead 
in  the  freezing  tank,  so  that  only  two  compartments  are  formed.  It 
would  be  better  to  increase  the  length  of  the  tank  so  that  additional 
bulkheads  could  be  inserted  to  divide  the  tank  into  eight  compart- 
ments, each  containing  four  double-face  cells  as  required  to  freeze 
a  day's  pull  of  ice. 


174  REFRIGERATION 

STORING   AND  SELLING  ICE 

Distribution  is  the  one  great  problem  of  the  ice  manufacturer. 
The  product  of  his  factory  is  perishable  and  cannot  be  held  except 
at  considerable  expense.  It  must  be  disposed  of  as  made  if  the  ledger 
is  to  show  a  profit.  Some  manufacturers,  it  is  true,  find  it  advisable 
to  have  a  smaller  plant  than  required  to  meet  the  demands  of  the 
summer  trade  and  arrange  to  run  all  the  year  round,  storing  up  the 
ice  made  during  the  winter  so  as  to  have  it  available  when  needed. 
The  cost  of  such  storage  is  about  as  much  as  the  interest  on  the  larger 
plant,  and  there  is  considerable  loss  of  the  ice  put  in  store  unless  it  is 
refrigerated.  This  necessitates  using  part  of  the  capacity  of  the 
machine  on  the  cooling  coils  of  the  storage  rooms.  Then  again  there 
is  no  opportunity  to  overhaul  the  plant  when  run  continuously  and 
the  item  of  depreciation  is  larger  than  it  should  otherwise  be.  On  the 
other  hand  the  best  machine  and  the  wisest  manager  cannot  regulate 
production  to  exactly  meet  demand,  for  two  successive  summer  days 
may  bring  very  different  demands  for  ice.  Some  days  the  manager 
has  ice  melting  on  his  hands  or  his  machine  killing  time,  while  at  other 
times  he  sits  up  nights  wondering  where  he  is  going  to  get  the  ice. 

All  things  considered  it  is  best  to  store  a  moderate  amount  of 
ice  and  have  a  medium-sized  plant,  arranging  things  so  that  there 
will  be  opportunity  to  overhaul,  repair,  and  repaint  the  system  during 
the  winter.  Ice  plants,  then,  are  usually  provided  with  a  temporary 
storage  room  and  a  larger  room  for  permanent  storage.  Any  over- 
plus of  production  from  day  to  day  goes  into  the  small  storage  room 
and  in  seasons  of  very  light  demand  practically  all^the  output  will  go 
into  the  large  store-room.  In  most  cases,  and  wherever  possible, 
it  is  best  to  have  the  storage  rooms  on  a  floor  level  lower  than  the  top 
of  the  tank  so  that  the  ice  can  be  passed  by  chute  to  the  stores. 
Otherwise  conveyors  are  used,  these  being  of  several  forms,  but  all 
built  on  the  endless  chain  plan.  A  chain  having  catch  lugs  passe? 
along  a  slot  in  the  floor  of  the  slide  or  chute  and  carries  the  ice  up 
to  the  storage  room.  In  storing  large  quantities  of  ice,  as  in  plants 
where  fruit  and  produce  cars  are  iced,  it  is  necessary  to  pack  the 
ice  in  tiers  and  for  more  than  two  tiers  some  form  of  hoisting  appa- 
ratus should  be  used  in  the  storage  room.  About  50  cubic  feet  of 
space  are  allowed  per  ton  of  ice  to  be  stored,  and  1  running  foot  of  If- 
inch  brine  piping  should  be  allowed  for  every  6  to  10  cubic  feet  of 


REFRIGERATION  175 

space,  depending  on  the  latitude  and  the  size  of  the  room.  Owing 
to  the  low  temperature  of  the  ice,  it  is  safe  to  allow  at  least  one- 
third  less  pipe-cooling  surface  than  is  provided  for  ordinary  stores. 
A  temperature  of  28  degrees  is  ample  to  prevent  melting  but  some 
authorities  prefer  to  carry  as  low  as  22  degrees,  for  they  consider 
the  low  temperature  keeps  the  ice  firm. 

Methods  of  packing  ice  vary,  some  preferring  to  allow  space  be- 
tween the  blocks  for  ventilation  and  others  packing  the  blocks  close  to- 
gether and  exactly  over  each  other  in  successive  tiers — i.e.,  no  break- 
ing of  joints — with  packing  material  provided  where  the  store-room 
is  not  to  be  cooled  artificially.  Where  spaces  are  left,  wood  spacing 
strips  are  placed  between  tiers  and  blocks  in  all  directions.  If  hard 
dry  ice  is  put  in  store  at  or  below  freezing  and  the  temperature  is 
kept  down — or,  even  packed  simply,  without  cooling  coils  in  the 
rooms — it  will  come  out  in  good  condition  without  the  strips,  which 
are  little  used  in  the  United  States.  The  rooms  should  have  ven- 
tilators so  that  all  foul,  damp  air  may  be  removed,  and  good  drainage 
should  be  provided.  In  permanent  store-rooms  good  insulation 
should  be  provided  and  this  is  done  almost  universally  in  ice  plants, 
there  being  no  need  of  packing  materials  except  in  the  case  of  natural 
ice  storage.  Materials  used  for  such  purpose  are  hay,  rice  straw  or 
chaff,  soft  wood  shavings,  sawdust,  and  similar  substances.  About 
six  inches  of  this  material  is  packed  around  the  walls  in  storing  ice 
where  cooling  coils  are  not  used.  Also  a  good  thick  layer  is  placed 
on  top  of  the  upper  tier.  When  coils  are  used  they  should  be  placed 
in  racks  hung  from  the  ceiling  and  provided  with  drip  pans  having 
proper  drainage  connections  to  the  sewer.  In  some  cases  it  is  neces- 
sary to  place  the  coils  on  the  walls  of  the  room. 

Where  ice  taken  from  the  stores  is  to  be  used  in  icing  cars,  it  is 
put  through  a  crusher  and  sent  by  barrow  or  chute  to  the  car  box. 
In  delivering  ice  to  the  retail  trade,  care  should  be  taken  to  be  regular 
and  systematic  in  all  arrangements  and  dealings  with  customers. 
Go  to  the  same  house  at  the  same  time  on  the  day  when  it  is  known 
that  ice  is  wanted  and  don't  go  any  other  time.  Endeavor  to  have 
the  men  satisfied  so  that  they  will  stay  on  the  job  long  enough  to 
learn  their  business  and  the  little  traits  of  the  customers.  Have 
everything  about  the  wagons  and  the  men  clean,  and  use  tested  scales 
with  the  coupon  system  of  selling.  Let  each  team  have  its  regular 


176  REFRIGERATION 

route  and  let  the  drivers  understand  that  they  are  responsible  for 
what  happens  on  their  respective  routes.  In  shipping  small  lots  of 
ice,  blocks  may  be  packed  in  sawdust  in  bags.  Where  car  loads  are 
to  be  shipped  get  refrigerator  cars  if  possible.  If  not,  pack  the  ice 
in  an  ordinary  car  with  sawdust  using  heavy  paper  around  the 
blocks  after  they  are  in  position  so  as  not  to  foul  the  ice  with  the 
dust.  The  paper  also  helps  to  keep  out  heat.  Suitable  hand  tools 
should  be  provided  in  plenty  as  they  are  worth  their  cost  several 
times  over  in  saving  the  time  of  drivers  and  help,  not  to  speak  of 
insuring  accurate  cut  of  ice  which  means  less  loss  and  better  satis- 
faction to  customers. 

ICE=PLANT  INSULATION 

The  most  important  piece  of  insulating  work  in  an  ice  plant  is 
on  the  freezing  tank.  Aside  from  this  the  ammonia  line  from  the 
tank  to  the  compressor  as  well  as  the  suction  headers,  where  ex- 
posed, and  all  brine  circulation  lines  should  be  insulated.  The 
steam  lines  should  be  covered  to  prevent  undue  radiation.  For 
this  purpose  a  good  magnesia  covering  should  be  employed.  For 
the  ammonia  and  brine  lines,  cork  pipe  covering  should  be  used. 
Cork  is  now  prepared  for  such  work  with  parts  made  to  fit  all  pipe 
fittings,  as  well  as  any  bends  and  turns.  Next  to  the  tank  in  impor- 
tance the  ice  storage  rooms  should  be  protected  with  insulating  ma- 
terial, more  or  less  care  being  used  in  this  work  depending  on  the  use 
to  which  the  room  is  to  be  put.  For  a  temporary  small  storage  it  is 
not  worth  while  to  spend  a  large  amount  of  money,  but  for  permanent 
storage  rooms  the  insulation  should  be  done  well.  This  may  be  done 
in  any  of  the  ways  usual  for  cold  storage  rooms,  care  being  taken  to 
provide  drainage  for  any  water  that  may  result  from  melting. 

Owing  to  the  dampness,  cork  insulation  finished  with  cement 
plaster  is  about  the  most  satisfactory  material  for  an  ice  storage  room. 
On  a  concrete  foundation,  from  4  to  6  inches  of  Acme  corkboard  is 
laid  in  cement,  coated  with  asphalt,  and  finished  over  by  laying  3 
inches  of  concrete  having  cement  finish  on  top.  The  ceiling  and 
walls  are  insulated  with  from  3  to  6  inches  of  corkboard  laid  in  Port- 
land cement,  with  asphalt  between  layers,  and  finished  with  Port- 
land cement  plaster.  This  method  of  insulation  gives  a  permanent 
water-proof  finish  and  is  effective  and  durable. 


REFRIGERATION  177 

Tank  Insulation.  There  are  a  number  of  ways  to  insulate  a 
tank  and  various  insulating  materials  that  may  be  used,  but  planer 
shavings,  when  perfectly  dry,  give  about  as  good  insulation  as  can 
be  had  at  moderate  cost.  Cork  is  better  but  is  more  expensive, 
though  by  using  it  in  granulated  form  for  the  sides  of  the  tank  the 
expense  is  reduced  considerably.  Other  manufactured  products 
are  too  expensive,  as  a  rule,  in  proportion  to  the  benefit  to  be  derived 
from  their  use.  Sawdust  lies  so  close  that  there  is  not  enough 
dead  air  space,  and  takes  up  water  readily  so  that  its  insulating 
properties  become  greatly  impaired.  Ground  tan  bark  is  subject 
to  the  same  objection.  Since  good  insulation  cuts  down  operating 
expenses,  it  is  economy  to  use  as  thorough  insulation  as  circum- 
stances permit.  This  does  not  necessarily  mean  the  most  expensive 
job  that  can  be  had.  Where  shavings  are  used,  the  thickness  be- 
neath the  tank  should  not  be  less  than  12  inches  and  on  the  sides  it 
should  be  at  least  10  inches,  greater  thickness  being  desirable  if 
space  can  be  had. 

Matched  flooring  is  used  for  partitions,  with  tarred  paper  laid 
on  the  flooring  when  in  place  to  make  it  air  tight.  A  simple  construc- 
tion is  obtained  by  coating  the  outside  surface  of  the  tank  with  as- 
phalt or  pitch,  and  pack  shavings  between  it  and  the  air-tight  wall 
built  up  of  matched  boards  on  studs  set  on  18-inch  centers.  In  the 
case  of  metal  tanks,  which  are  used  almost  universally  in  preference 
to  wood,  a  layer  of  pitch  and  1  or  2  inches  of  shavings  should  be  laid 
on  the  floor  so  as  to  form  a  cushion  on  which  the  tank  sets,  thus  pre- 
venting possible  strain  due  to  irregularities  of  surface.  Although  wood 
tanks  have  been  in  use  for  some  time  and  cement  has  more  recently 
come  into  use  as  a  material  for  tank  construction,  neither  of  these  ma- 
terials may  be  considered  as  satisfactory  in  all  respects  as  the  steel 
tank.  More  framing  must  be  used  with  the  wooden  tank  to  withstand 
the  pressure  of  the  water  and  great  care  must  be  taken  to  make  the 
cement  or  concrete  tank  waterproof.  For  plate  plants,  the  freezing 
tanks  are  commonly  constructed  of  wooden  compartments,  the  framing 
being  made  ample  to  withstand  the  pressure.  Where  the  water  is 
bad  and  it  is  necessary  to  wash  out  the  freezing  compartments  often, 
it  is  well  to  have  each  compartment  insulated  from  the  others. 

Cork  insulation  is  largely  used  on  tanks,  owing  to  its  waterproof 
qualities  and  the  fact  that  it  requires  much  less  space  than  other  in- 


178  REFRIGERATION 

sulation.  Where  this  material  is  used,  the  foundation  on  which  the 
tank  is  to  be  made  is  constructed  of  concrete,  preferably  laid  on 
cinders,  on  top  of  which  Acme  corkboard  is  laid  in  Portland  cement. 
This  insulation  is  from  3  to  6  inches  thick  and  is  coated  on  top  with 
asphalt,  the  tank  being  set  directly  in  the  asphalt.  The  sides  are 
then  insulated  with  Acme  or  Nonpareil  board  laid  on  in  cement, 
with  asphalt  between  layers  and  finished  outside  with  Portland  cement 
plaster.  This  insulation  is  usually  about  6  inches  thick  and  is  quite 
as  effective  as  the  thicker  insulating  walls  made  with  other  materials. 
Where  it  is  desired  to  reduce  expense,  and  space  is  of  no  particular 
account,  regranulated  cork  may  be  used  around  the  sides  packing 
it  between  the  tank  and  a  wooden  wall,  as  in  the  case  of  shavings. 

GENERAL  COLD  STORAGE 

After  ice-making,  cold  storage  is  the  most  important  and  widely 
used  application  of  mechanical  refrigeration.  By  means  of  low 
temperatures,  fruits  and  perishable  products  may  be  preserved  dur- 
ing periods  of  plenty  until  such  time  as  the  supply  falls  off  and  the 
demand  increases,  when  the  products,  coming  from  store  in  good 
condition,  may  be  sold  at  a  profitable  figure.  Thus  decay  is  pre- 
vented, the  product  is  preserved  in  its  natural  form — quite  another 
matter  from  goods  preserved  by  drying  or  salting — and  the  dealer 
is  able  to  make  a  profit.  The  producer  at  the  same  time  is  able  to 
market  his  crops  to  better  advantage  than  when  all  the  goods  have 
to  be  sold  on  a  glutted  market.  Owing  to  the  fact  that  the  period 
of  consumption  for  any  given  product  is  greatly  increased,  produc- 
tion can  be  increased  accordingly  with  a  corresponding  increase  in 
profits  to  the  farmer  and  fruit  grower.  The  owner  of  perishabb 
goods  is  not  compelled  to  market  them  for  fear  that  they  may  spoil 
but  may  choose  his  market  and  hold  his  goods  irrespective  of  time 
and  distance. 

For  these  reasons,  cold  storage  establishments  are  coming  into 
use  the  country  over.  Refrigerator  cars  make  possible  the  shipping 
of  goods  to  distant  markets  where  good  prices  prevail,  and  in  case 
markets  are  not  satisfactory  in  the  country  of ,  production,  goods 
may  be  exported  in  carefully  constructed  storage  rooms  on  board 
the  large  steamers.  Thus  it  is  possible  to  place  perishable  products 
in  the  hands  of  consumers  in  such  quantity  and  at  such  time  as  the 


REFRIGERATION  179 

owner  desires  so  that  the  market  conditions  are  steady  and  the  con- 
sumer is  able  to  obtain  articles  of  food  that  could  not  be  had  without 
the  aid  of  refrigeration.  Meats  produced  in  Australia  are  shipped 
to  England  and  fruits  grown  in  California  are  sold  in  New  York  and 
Europe.  On  a  bleak  winter  day  one  may  have  the  freshest  vege- 
tables and  fruits  on  his  table,  in  any  part  of  the  world.  Peaches  grown 
in  Australia  have  been  served  at  millionaire  feasts  in  New  York 
during  the  months  of  January  and  February.  Apples,  butter,  eggs, 
and  other  such  products  are  sent  abroad  by  the  ship-load.  In  a  word 
there  is  no  perishable  product  that  cannot  be  handled  to  advantags 
by  means  of  refrigeration. 

But  food  products  are  not  the  only  things  kept  in  cold  storage. 
Many  articles  not  classed  as  perishable  are  kept  at  low  temperatures. 
Furs,  for  example,  are  placed  in  storage  to  prevent  damage  from 
moths  and  to  preserve  the  skins.  On  coming  out  of  store  the  luster 
of  the  furs  is  greatly  improved,  the  articles  becoming  more  valuable 
in  some  cases  than  before  storage.  Clothing  and  woolens  are  also 
stored.  Dried  fruits  are  kept  during  the  warm  months  of  summer. 
Seedsmen  find  it  profitable  to  store  their  stock  so  as  to  prevent  deteri- 
oration by  the  seed  drying  out,  owing  to  evaporation  of  the  oils. 
Thousands  of  dollars  are  saved  in  this  way,  as  the  germinating  value 
of  the  seed  may  be  kept  unimpaired  and  the  seedsman  has  good 
insurance  against  failure  of  any  year's  crop.  Peanuts,  walnuts, 
and  other  like  goods  are  carried  through  the  summer  and,  during 
^he  winter,  potatoes  and  cabbage  are  put  in  store.  Each  year  some 
new  product  is  added  to  the  list  of  articles  carried  in  cold  stores  and 
there  seems  to  be  no  limit  to  the  growth  of  the  ever-widening  field  for 
the  cold  storage  industry. 

Conditions  for  Preservation.  In  any  cold  storage  room,  three 
things  are  essential  if  the  goods  are  to  be  cared  for  properly.  The 
air  in  the  rooms  should  be  renewed  frequently  by  a  good  system  of 
ventilation;  all  air  entering  the  rooms  should  contain  an  amount 
of  moisture  suitable  to  the  temperature  and  the  goods  carried;  and 
the  temperature  should  be  suited  to  the  given  products,  not  varying 
outside  of  certain  limits.  A  hygrometer  is  used  for  measuring  the 
amount  of  moisture  in  the  air  and  this  should  be  done  accurately 
as  too  little  moisture  will  cause  the  goods  to  be  damaged  by  evapora- 
tion, while  too  much  moisture  will  cause  mold  to  be  formed.  One 


180  REFRIGERATION 

of  these  evils  is  about  as  bad  as  the  other.  Products  that  are  dried 
to  the  mere  fibre  are  of  no  value  for  food  and  those  that  are  musty 
are  not  palatable.  The  lower  the  temperature,  the  less  moisture  the 
air  can  carry  and  if  the  air  is  brought  into  the  rooms  with  more  moist- 
ure than  corresponds  to  the  amount  it  can  carry  at  the  temperature 
of  the  room,  the  excess  will  be  condensed  and  form  ice  on  the  pipes 
and  other  places.  This  frost  should  be  kept  off  the  pipes — where 
pipe  coolers  are  used  in  the  rooms — as  far  as  possible,  as  ice  is  a  good 
insulator  and  prevents  the  heat  being  absorbed  by  the  gas  or  brine 
in  the  pipes.  The  temperature  is  entirely  under  the  control  of  the 
operator  and  can  be  raised  or  lowered  at  will  by  circulating  more 
brine  or  expanding  more  gas,  according  to  the  system  used. 

There  is  a  wide  difference  of  opinion  among  authorities  as  to 
the  temperatures  required  for  the  best  results  with  different  products. 
A  number  of  conditions  complicate  the  question  so  that,  except  for 
a  few  of  the  articles  most  handled,  no  definite  rule  can  be  laid  dowrn. 
Where- the  goods  have  been  shipped,  consideration  must  be  taken  of 
the  temperature  before  and  during  shipment  and  particularly  whether 
or  not  the  temperature  has  been  excessively  high  or  low  at  any  time 
during  shipment.  Furthermore  the  condition  of  the  goods  must  be 
taken  into  account,  and  the  time  they  are  to  be  kept  in  store,  as  well 
as  the  purpose  for  which  they  will  be  used  when  taken  out  of  store. 
Thus  for  example,  if  decay  has  set  in  with  a  shipment  of  peaches 
which  is  being  unloaded  into  the  storage  rooms  and  they  are  to  be 
kept  only  a  short  time  and  then  disposed  of  at  whatever  the  market 
will  stand,  it  would  be  well  to  get  the  temperature  down  as  quickly 
as  possible  to  that  required  for  keeping  this  fruit — the  lower  working 
limit  being  preferable.  On  the  other  hand  if  it  is  a  shipment  of  sound 
fruit  that  is  to  be  kept  some  time,  one  could  do  better  to  work  at  a 
higher  temperature  and  cool  the  fruit  more  gradually,  it  being  re- 
cognized, of  course,  that  under  such  conditions  the  refrigeration  can 
be  done  more  economically.  In  both  these  cases,  the  moisture  in 
the  air  in  a  given  cold  room  would  have  a  considerable  bearing  on 
the  course  pursued. 

Where  certain  rooms  are  used  for  commission  trade  with  goods 
being  taken  in  and  out  at  frequent  intervals,  the  refrigeration  must 
be  more  effective  than  for  the  same  class  of  goods  stored  over  a  long 
period  of  time.  Altitude  and  local  conditions  affect  the  case  to  a 


REFRIGERATION 


181 


TABLE   XXI 
Temperatures  for  Cold  Storage  of  Products 


PRODUCTS 


DEO.  F. 


PRODUCTS 


DEO.  F. 


Apple  butter 42 

Apples ' 30 

Asparagus 33 

Bananas 45 

Beans  (dried) 45 

Beer  (bottled) 45 

Berries,  fresh  (few  days  only)  ....  40 

Buckwheat  flour 42 

Butter 14 

Butterine 20 

Cabbage 33 

Canned  fruits .  .  40 

Canned  meats 40 

Cantaloupes  (one  to  two  months)  33 

Cantaloupes  (short  carry) 40 

Carrots 33 

Caviar 36 

Celery 32 

Cheese  (long  carry) 35 

Chestnuts 34 

Chocolate  dipping  room 65 

Cider _ 32 

Cigars 42 

Corn  (dried) 45 

Corn  meal 42 

Cranberries 33 

Cucumbers 38 

Currants  (few  days  only) 32 

Cut  roses 36 

Dates 55 

Dried  beef 40 

Dried  fish 40 

Dried  fruits 40 

Eggs 30 

Ferns 28 

Field  grown  roses 32 

Figs 55 

Fish,  fresh  water  (after  frozen). .  .  18 

Fish,  nt  frozen  (short  carry)  ....  28 

Fish,  salt  water  (after  frozen)  ....  15 

Fish  (to  freeze) 5 

Frogs  legs  (after  frozen) 18 

Fruit  trees 30 

Fur  and  fabric  room 28 

Furs  (undressed) 35 

Game  (after  frozen) 10 

Game  (short  carry) 28 

Game  (to  freeze) 0 

Ginger  ale 36 

Grapes 36 

Hams  (not  brined) 20 

Hogs 30 

Hops 32 


Huckleberries  (frozen,  long  carry) 

Japanese  fern  balls 

Lard 

Lemons  (long  carry) 

Lemons  (short  carry) 

Lily  of  the  valley  pips 

Livers 

Maple  sugar 

Maple  syrup 

Meat,  fresh  (ten  to  thirty  days)  . 

Meats,  fresh  (few  days  only) 

Meats,  salt  (after  curing) 

Mild  cured  pickled  salmon 

Nursery  stock 

Nuts  in  shell 

Oatmeal 

Oils 

Oleomargarine 

Onions 

Oranges  (long  carry) 

Oranges  (short  carry) , . 

Oxtails 


Oysters,  iced  (in  tubs) 

Oysters  (in  shell) 

Palm  seeds 

Parsnips 

Peach  butter 

Peaches  (short  carry) 

Pears 

Peas  (dried) 

Plums  (one  to  two  months) 

Potatoes 

Poultry,  (after  frozen) 

Poultry,  dressed  (iced).  ........ 

Poultry  (short  carry) 

Poultry  (to  freeze) 

Raisins 

Ribs  (not  brined) 

Salt  meat  curing  room 

Sardines  (canned) 

Sauerkraut ...       


casings 

Scallops  (after  frozen) 

Shoulders  (nt  brined) 

Strained  honey 

Sugar 

Syrup 

Tenderloin,  etc 

Tobacco 

Tomatoes  (ripe) 

Watermelons  (short  carry) 

Wheat  flur 

Wines 


20 
31 
40 
38 
60 
29 
20 
45 
45 
30 
35 
43 
33 
30 
40 
42 
45 
20 
32 
34 
50 
30 
35 
43 
38 
32 
42 
50 
33 
45 
32 
34 
10 
30 
28 
0 
55 
20 
33 
40 
38 
20 
16 
20 
45 
45 
45 
33 
42 
42 
40 
42 
50 


182  REFRIGERATION 

certain  extent  and  the  best  rule  for  the  practical  man  is  to  study  his 
own  plant  and  the  conditions  prevailing;  being  careful  particularly 
to  see  that  his  thermometers  are  correct  so  that,  when  he  finds  some 
unusual  temperature  the  best  for  a  certain  article  in  his  plant,  it  will 
not  be  due  to  error  in  his  instrument.  As  a  rough  guide  to  be  used 
where  no  other  information  for  the  particular  plant  is  available, 
Cooper  gives  the  temperatures  shown  in  Table  21,  which,  however, 
should  be  used  with  caution.  Other  authorities  give  figures  varying 
anywhere  up  to  10  degrees  from  the  data  in  this  table,  but  on  the 
whole  the  table  may  be  considered  about  the  least  arbitrary  of  all 
and  is  based  in  the  main  on  figures  taken  from  practice. 

INSULATION 

In  considering  this  topic,  the  student  should  recall  the  discussion 
of  heat  in  the  first  part  of  this  paper,  where  it  was  shown  that  heat 
is  transmitted  in  three  ways — by  convection,  by  radiation,  and  by 
conduction — the  transmission  taking  place  in  all  three  of  these  ways 
in  cold  storage  plants.  Owing  to  the  low  temperatures,  however, 
there  is  comparatviely  little  transmission  in  storage  rooms  by  radia- 
tion, and  practically  all  heat  passes  into  the  rooms  by  the  process  of 
conduction.  Where  air  space  insulation  is  used  there  is  consider- 
able transmission  by  convection  currents  in  the  manner  explained 
already  and  this  is  the  principal  reason  why  air  space  insulation  is 
inefficient  as  compared  with  the  other  methods  of  insulating.  When 
it  is  considered  that  from  one-half  to  seven-eighths  of  the  refrigera- 
ting work  in  a  storage  plant  is  required  to  remove  the  heat  that  leaks 
through  the  walls,  the  importance  of  good  insulation  is  seen.  The 
increase  in  cost  for  insulating  work  well  done  is  insignificant  as 
compared  with  the-  resulting  decrease  in  operating  cost.  On  the 
other  hand,  the  cheaper  insulation  is  less  permanent  and  demands 
a  larger  amount  of  coal  to  drive  the  refrigerating  machinery  to  keep 
out  the  heat  from  the  rooms,  which  could  have  been  excluded  with 
effective  insulation. 

If  a  perfect  insulation  could  be  had  there  would  be  no  need  of 
refrigerating  machinery  except  to  cool  the  rooms  down  in  the  first 
place  and  to  remove  any  heat  admitted  by  opening  doors  for  taking 
goods  in  and  out  of  store.  Such  a  condition  is  impossible,  however, 
as,  owing  to  the  nature  of  heat,  it  is  not  possible  to  wholly  prevent 


REFRIGERATION  183 

an  increase  in  the  rate  of  vibration  in  a  body  that  has  contact  with 
a  hotter  body  in  which  the  rate  of  vibration  is  more  rapid.  Differ- 
ent rates  of  vibration  tend  to  become  equalized  in  adjacent  bodies 
just  as  naturally  as  water  tends  to  run  down  hill.  Different  mater- 
ials have  varying  capacities  for  hindering  or  retarding  such  vibra- 
tion but  no  matter  what  the  material  or  how  thick  the  walls, 
some  transmission  will  take  place  until  finally  the  temperatures 
on  the  two  sides  of  the  wall  will  be  equal.  During  the  past  cen- 
tury scientists  have  made  many  laboratory  tests  as  to  the  heat- 
transmitting  qualities  of  various  insulating  materials,  but  in  most 
cases  these  results  are  of  little  value  to  refrigerating  men  on  account 
of  the  fact  that  the  experiments  were  mostly  performed  with  high 
differences  in  temperature  and  dry-air  conditions,  as  for  the  insula- 
tion of  steam  pipes  where  the  temperature  difference  is  at  least  275 
degrees.  These  conditions  do  not  apply  for  the  low  temperatures  and 
moist  air  met  in  refrigerating  establishments  and  it  is  usually  the  case 
that  a  good  insulator,  for  the  conditions  named,  is  a  decidedly  poor  one 
under  the  conditions  prevailing  in  cold  storage  establishments. 

Non=Conductors.  To  be  a  good  insulator  a  material  should 
have  poor  conducting  power  at  low  temperatures  or  with  small  tem- 
perature differences,  and  should  have  a  high  specific  heat  and  high 
specific  gravity.  The  higher  the  product  of  the  two  last  items,  the 
more  valuable,  other  things  being  equal,  is  the  insulation.  As  an 
example  take  a  cubic  foot  of  air  and  a  cubic  foot  of  flake  charcoal 
used  as  insulation.  The  air  weighs  0.0807  pound  and  since  its 
specific  heat  is  0.237  it  will  require  0.0191  B.  T.  U.  to  increase  its 
temperature  1°  F.  For  charcoal,  the  figures  for  weight,  specific  heat,  and 
heat  required  for  1  degree  rise  of  temperature  are  11.4,  0.242  and  2.758 
respectively.  In  case,  then,  the  machinery  should  be  stopped  for 
any  reason,  the  insulating  material  would  have  to  be  heated  up  be- 
fore the  temperature  in  the  storage  rooms  could  rise,  the  amount  of 
heat  absorbed  by  the  insulation  itself  being  in  proportion  to  the  pro- 
duct just  mentioned.  In  other  words  for  each  degree  rise  in  temper- 
ature in  the  rooms  the  cubic  foot  of  air  must  absorb  only  0.0191 
B.  T.  U.  while  the  charcoal  must  absorb  2.758  units.  This  is  the 
reserve  power  of  the  insulation  and  is  of  considerable  importance, 
though  it  may  be  overbalanced  by  the  conductivity  of  a  materal  if 
this  be  high. 


184 


REFRIGERATION 

TABLE  XXII 

Non-Conducting  Power  of  Substances 


NON-CONDUCTORS  ONE  INCH  THICK 

NET  CUBIC  IN. 
OF  SOLID 
MATTER  IN   100 

HEAT  UNITS  TRANS- 
MITTED PER  SQ.  FT. 
PER  HOUR 

Still  air  

43 

Confined  air  

108 

Confined  air  =  310°  

203 

Wool  =  310°  

4.3 

36 

Absorbent  cotton  
Raw  cotton  
Raw  cotton  
Live-geese  feathers  =  310°  
Live-geese  feathers  =  310°  
Cat-tail  seeds  and  hairs  

2.8 
2 
1 
5 
2 
2  1 

36 
44 
48 
41 
50 
50 

Scoured  hair,  not  felted  
Hair  felt  

9.6 
8  5 

52 
56 

Lampblack  =  310°  
Cork  ground 

5.6 

41 
45 

Cork  solid 

49 

Cork  charcoal  =  310°  
White-pine  charcoal  —  310° 

5.3 
11  9 

50 

58 

Rice-chaff  

14.6 

78 

Cypress  (  Taxodiuin)  shavings  

7 

60 

Cypress  (  Taxodium)  sawdust  
Cypress  (  Taxodium}  board  

20.1 
31.3 

84 
83 

Cypress  (Taxodium)  cross-section  
Yellow  poplar  (Liriodendron)  sawdust... 
Yellow  poplar  (Liriodendron)  board  
Yellow  poplar  (Liriodendron)  cross-sec.. 
"Tunera"  wood,  board  
Slag  wool  (Mineral  wool)  
Carbonate  of  magnesium  

31.8 
16.2 
36.4 
30.4 
79.4 
5.7 
6 
2  3 

145 

75 
76 
141 
156 
50 
50 
52 

"Magnesia  covering,"  light  
"Magnesia  covering,"  heavy  

8.5 
13.6 

58 
78 

Fossil  meal  =*=  310^  

6 

60 

Zinc  white  —  310°  

8.8 

72 

Ground  chalk  =  310°  
Asbestos  in  still  air  
Asbestos  in  movable  air  
Asbestos  in  movable  air  =  310°  
Dry  plaster  of  paris  =  310°  
Plumbago  in  still  air  
Plumbago  in  movable  air  =  310°  
Coarse  sand  =  310°  
Water,  still  

25.3 
3 
3.6 
8.1 
36.8 
30.6 
26.1 
52.0 

80 
56 
99 
210 
131 
134 
296 
264 
335 
345 

290 

251 

Glycerin,  
Castor  oil,  '  
Cotton-seed  oil,  "  
Lard  oil,  "  
Aniline,  '  
Mineral  sperm  oil,  "  
Oil  of  Turpentine,  "  

197 
136 
129 
125 
122 
115 
95 

RFFRIGFPATION  185 

Ordway  gives  the  data  in  Table  22  for  the  non-conducting  power 
of  various  substances,  the  figures  being  determined  from  insulation 
tests  on  steam  pipes  where  the  difference  in  temperature  on  the  two 
sides  of  a  1-inch  thickness  of  the  substances  was  100  degrees.  Where 
not  stated  in  the  table,  the  source  of  heat  was  water  at  about  176°  F., 
but  in  some  cases  steam  at  a  temperature  of  310°  F.  was  used.  It 
will  be  noted  in  the  table  that  still  air  is  one  of  the  poorest  conductors 
of  heat,  but  if  a  body  of  confined  air  is  arranged  to  allow  the  set- 
ting up  of  convection  currents  as  before  mentioned,  the  air  is  ren- 
dered a  much  better  conductor.  It  is  to  prevent  these  currents, 
that  the  air  is  confined  in  spaces  small  enough  to  keep  it  still,  and 
the  value  of  most  insulators  is  determined  by  the  effectiveness  with 
which  they  prevent  the  air  from  moving  by  separating  it  into  such 
small  particles  that  its  viscosity  is  too  great  to  allow  of  movement. 

Experiments  have  been  made  to  determine  the  amount  of  heat 
conduction  through  a  vacuum,  with  results  that  tend  to  indicate  a 
much  smaller  rate  of  conduction  than  through  still  air.  In  laboratory 
experiments  liquid  air  when  placed  in  a  glass  vessel  surrounded  by 
a  vacuum  retained  its  liquid  form  for  several  days,  but  no  success- 
ful scheme  for  applying  a  vacuum  in  practical  insulation  work  has 
yet  been  evolved.  It  has  generally  been  assumed  that  the  rate  of 
heat  transmission  is  in  proportion  to  the  difference  of  temperature 
on  the  two  sides  of  a  wall  and  inversely  proportional  to  the  thickness 
of  the  material;  but  recent  experiments  go  to  show  that  the  rate  of 
transmission  increases  wTith  increase  of  temperature  difference  and 
that  it  does  not  decrease  exactly  in  inverse  proportion  with  increase 
of  thickness.  As  most  coefficients  of  heat  transmission  are  deter- 
mined with  a  temperature  difference  of  1  degree,  it  is  obvious  that 
they  cannot  be  correct  for  much  larger  differences  and  should  in 
fact  be  increased  by  at  least  50  per  cent  in  practical  calculations. 
With  the  constant  tendency  toward  the  use  of  lower  temperatures 
in  cold  storage  and  general  refrigeration  work,  this  matter  becomes 
of  first  importance.  In  some  cases  the  temperature  difference  may 
be  as  much  as  90°  F. 

Aside  from  the  loss,  incident  to  using  poor  insulating  material 
by  reason  of  the  heat  that  must  be  removed,  there  are  other  disad- 
vantages that  must  be  taken  into  consideration.  The  heat  admitted 
through  poor  insulation  raises  the  temperature  of  the  outer  parts  of 


186  REFRIGERATION 

a  room  near  the  walls  so  that  it  is  impossible  to  keep  all  parts  of  the 
store  at  the  same  temperature.  This  is  undesirable  in  many  respects 
and  for  fear  of  freezing  the  goods  near  the  cooling  pipes  or  air  ducts, 
it  often  happens  that  the  temperature  is  carried  too  high  for  best 
results.  On  the  score  of  conductivity,  the  choice  of  insulators  is 
limited  to  vegetable  and  animal  substances.  In  selecting  one  of 
these  a  number  of  practical  considerations  must  be  taken  into  ac- 
count. The  material  should  be  odorless  so  as  not  to  taint  the  goods 
and,  as  far  as  possible,  should  be  proof  against  moisture.  In  case 
it  gets  wet,  it  should  not  be  of  such  nature  as  to  rot  easily.  It 
should  have  no  tendency  to  spontaneous  conbustion  and  should  be 
elastic  so  that  it  can  be  packed  er,ough  to  avoid  settling.  Aside  from 
these  things,  the  material  should  be  reasonably  cheap  and  easy  to 
apply  in  general  work,  and  should  be  vermin  proof.  As  far  as  pos- 
sible the  insulation  should  be  waterproof  and  fireproof,  but  as  none 
of  the  vegetable  and  animal  materials  have  these  qualities,  special 
measures  must  be  taken  to  make  the  finished  work  proof  against  fire 
and  water.  This  is  done  by  masonry  work  and  cement  plaster. 

For  practical  purposes,  the  choice  of  an  insulating  material 
will  be  restricted  to  cork,  dry  shavings,  mineral  wool,  or  hair  felt. 
Tarred  papers  are  used  on  the  board  work  used  to  retain  the  insula- 
ting material  in  place  and  each  of  the  materials  named  may  be  used 
in  a  number  of  combinations  and  forms.  In  brick  buildings  it  is 
customary  to  use  a  hollow  tile  course  in  the  walls,  or  rather  to  lay 
such  tile  in  the  wall  so  as  to  form  a  moisture  barrier.  Two  such 
arrangements  are  shown  at  the  top  of  Fig.  79,  which  shows  a  number 
of  composite  insulation  structures,  tested  by  the  Fred  W.  Wolf  Co. 
Several  other  combinations  arranged  and  tested  by  Madison  Cooper 
are  shown  in  Fig.  80.  In  both  these  illustrations  the  figures  at  the 
right  represent  the  number  of  B.  T.  U.  transmitted  per  square  foot 
per  day  per  degree  difference  of  temperature.  It  will  be  noted  that 
in  all  cases  the  air-space  insulation  makes  a  poor  showing  as  com- 
pared with  other  forms,  especially  in  view  of  the  care  and  attention 
necessary  to  construct  it  properly.  It  is  almost  impossible  to  get 
workmen  that  will  give  proper  attention  in  putting  together  the 
timber  work  for  such  insulation  so  that  it  will  be  tight,  and  much  of 
the  complaint  with  cold  stores  in  the  past  has  been  due  to  air  leaks 
resulting  from  such  neglect. 


3"  SCRATCHED  HOLLOW  TILES. 
4" SPACE  FILLED  WITH 
MINERAL    WOOL. 

CEME.HT  PLA  5  TER. 


m 


B.T.U 


0.70 


FLOOR  CONSTRUCTION    -FIREPROOF. 


-3"FRAME 

PLAN  OF  WALL. 


DRY  CIHDER  F/tLIHG. 


DOUBLE  5P/ICE  HOLLOW  TILE 

ARCHES. 
\^  CEME/1T  PLASTER. 


BRICK  WALL. 


IR  SPACE. 
Va"0.&M.  BOARDS. 
WATERPROOF-  PAPER. 
4-5PACE  FILLED  WITH 

MINERAL  WOOL. 
•/"AIR  SPACE. 

7/e°D.e.n  BOARDS. 


•SIDING. 

WATERPROOF  PAPER. 

7/s-BOARDS. 

Z"X6"  STUDS-16"  O.C. 

4" SPACE  FILLED  WITH 

MINERAL  WOOL. 
WATERPROOF  PAP£R. 
7/a'BOARDS. 
?"AIR  SPACE. 


0.70 


1.74 


2.90 


DOOR 


7/a  "BOARDS. 
WATERPROOF  PAPfR. 
2"  SPACES  FILLED  W/TH 

MINERAL  WOOL. 
JOISTS. 
7/a  "BOARDS. 
WATERPROOF  PAPER. 


Vt»  PLANK  FLOORING, 
•^r'/a"  BOARDS. 

/WA  TERPROOF  PAPERS. 
"  ~-4"5PACe  FILLED  WITH 

.......  ......    ....^ Km*-*  ..-.-^-. -••    ......  ••-i.tfc.YM.  '  -••    ^      MINERAL   WOOL. 

-^m^^^r^^i^mr:--^^,  •  •  r "-   ;,  'fe^-^^  ^"BOARDS. 

.':^-i»  .V-:v''^;-Sr.^S;^i?v--'.-.--:  -v-  ^Pf^^  ^"/r^"  BEDDED  m DRY 

^v^V^'/f'v-^^^^K^-^'-V^:'  •••  -.v       *  •,  !cr- '-—.^t C/HDER  FILLII 


FILLING  IS  "HIGH. 


FLOOR  CONSTRUCTION. 

Fig.  79.    Composite  Insulation  Tested  by  Fred  W.  Wolf  Co. 


E.I7 


I.9E 


V&"D.&N.  BOARDS. 


14-  -  '/2  •  AIR  SPACES 

WATERPROOF  PAPERS. 


Ve'O.&M.BOAROS. 


ET.U 


3  1  6 


NO.l. 


j^i^^^^=^*^-^^^^-  '0. 


N0.8. 


..-.•••;-;-  •.•..•:..•.'..•:•••••.  .  .  : 


N0.3. 


Vfr  •/;//?  SPACES 
WATERPROOF  PAPERS. 
D.&M.  BOARDS. 


-  We"  D.&M.  BOARDS. 
'  •  W.KPAPfR. 

4"MIHERAL  WOOL. 
•  W.P.PAPfR. 
—  7/e' &  &M.  BOARDS. 


4.27 


3.46 


N0.4. 


i"  0.$  fit.  BOARDS. 
^T",    -W.P.PAPfR. 
V&'fr-—4"MILl  SHAVIHGS, 
'gZ&L*^  W.P.PAPfR. 

—  Va'D.&M.BOARDS. 


Z.95 


N0.8.. 


NO.  10. 


JSO.Il. 


7/a'D.8.M.  BOARDS. 

W.P.  PAPfR. 

3"5HEfT  CORK  -/"5H££T5. 

W.P.  PAPER. 

•>/a"O.&M.BOARDS. 


7/a"D.&M.BO/}RDS. 

W.P.PAPfR. 

WD.&M.BO/tRDS. 


W.P.  PAPfR. 
Va"D.&M.  BOARDS. 


W.P.  PAPER. 

3  "HAIRFEi.  T  - 1"  SHEETS. 

-  W.P.  PAPER.      . 

-  WD.&M.BOffRDS. 


7/e"  D.8.M.  BOARDS. 
W.P.PAPfR. 
I"  HAIR  FELT. 
W.P.  PAPER. 


Va'D.SiM.BOARDS. 

W.P.PAPfK. 

I"  SHEET  CORK. 

W.P.  PAPER.. 

7/a  "£>.  &M.  BOARDS. 


"^>.&.M.BOARD5. 
/"AIR  SPACE.. 

s^r  W.P.PAPER. 

^  %  "/?.  <S//^  BOARDS. 


11.06 


2.61 


1.88 


Pig.  80.    Insulation  Tests  of  Cooper. 


Ve"O.&M  BOARDS. 
Z"h 'AIR  FELT.  CORK  OR  MINERAL  WOOL 
WATERPROOF  PAPERS.  SLOCK, 

-r/e" SURFACE  BOARDS. 


Va"D.a.M.BOARD5. 

/  WA  TER PROOF  PAPER. 

7/a"  SURFACE  BOARDS. 

2"I~IAIRFELT.  CORKOK 
MINERAL  WOOL  BLOCK. 
V8"  SURFACE  BOARDS. 
WATERPROOF  PAPfRS. 


PARTITION 

'O.&.M  BOARDS. 
/"HAIR  FEL  T,  CORK  OR 

MlflERAL  WOOi  BLOCK. 
WATERPROOF  PAPER5. 
Ve"  SURF.  BOARDS. 


GRADE 


r/S  "D.  &,M.  BOARDS. 
^" HAIR FELT,  CORK  OR 

MINERAL  WOOL  BLOCK. 
WATERPROOF  PAPERS. 
Vs"  SURFACE  BOARDS. 
WATERPROOF  COATING. 


I"X2"  FURRING  SET 
VERTICAL  24" APART  BE- 
TWEEN HAIR  FELT.  CORK  OR 
MINERAL  WOOL  BLOCK. 


INTERMEDIATE   FLOOR 


WATERPROOF  PAPER. 
%>«  SURFACE  BOARDS. 
2"  HAIR  FELT.  CORK  OR 
MINERAL  WOOL  BLOCK. 
WATERPROOF  PAPER . 
Va" SURFACE  BOARDS. 
WATERPROOF  PAPER 


BA5EMENT  FLOOR 

"Va'iD.&M.  BOARDS. 

WATERPROOF  PAPER. 

7/e"  SURFACE  BOARDS. 

HAIR  FELT.  CORK  OR  MINERAL  WOOL  BLOCK. 
'•fVLLED  JPACf. 

WATERPROOF  COATING. 

—  DAMP  COURSE. 


SECTION   OF  INSULATION 


FINISHED  JAMB. 

/"CORK,  HAIR  FELT  OR 
MINERAL   WOOL  BLOCK. 
WATERPROOF  PAPER. 
13/4."  FRAME. 


DOOR 


BRICK  WALL 


PLAN  OF  INSULATION 
Fig.  81.    Cooper's  Method  of  Insulating  Buildings. 


190  REFRIGERATION 

Various  methods  of  applying  insulation  to  buildings  are  in  use. 
Fig.  81,  illustrating  the  construction  designed  by  Madison  Cooper, 
may  be  considered  as  representative  of  the  best  modern  practice  for 
ordinary  cold  storage  buildings.  The  walls  are  made  waterproof 
with  asphalt  or  similar  material;  the  filling  material,  either  shavings, 
granulated  cork,  or  mineral  wool,  is  placed  against  the  wall.  The 
sheathing  and  paper  are  arranged  in  courses  inside  as  shown  in  the 
figure.  An  8-inch  filled  space  with  4  inches  of  sheathing  etc.,  gives 
the  insulation  for  30  degrees.  A  total  thickness  of  13  inches  is  about 
right  for  20  to  25  degrees,  and  for  sharp  freezers  the  filled  space  should 
be  10  inches  with  an  additional  thickness  of  sheet  material.  This 
form  of  insulation  is  compact  and  durable,  the  indestructible  mater- 
ials such  as  waterproof  paper,  sheet  cork,  mineral  wool  block,  etc.,  be- 
ing placed  inside  where  the  conditions  are  most  severe.  In  many 
storage  houses  constructed  within  the  last  five  years,  sheet  cork  is 
used  exclusively,  being  laid  in  cement  directly  on  the  brick  walls  in 
one  or  more  layers  as  desired  and  finished  over  inside  with  waterproof 
cement  after  the  manner  already  mentioned  for  ice  storage  rooms. 

In  packing  any  filling  material,  due  regard  should  be  had  to 
getting  it  compact  enough  to  preclude  the  possibility  of  settling,  but 
at  the  same  time  not  too  dense,  especially  in  the  case  of  those  sub- 
stances which  are  fairly  good  conductors  in  the  natural  state.  Where 
the  building  regulations  of  cities  require  fireproof  construction,  the 
problem  of  insulation  is  much  complicated  and  it  is  difficult  to  con- 
struct any  effective  insulation  at  moderate  cost.  About  the  most 
practical  construction  is  the  use  of  corkboard  cemented  direct  on  the 
brick  or  tile  walls  and  ceilings  as  already  mentioned.  Plaster-of -Paris 
blocks  have  been  tried  as  a  fireproofing  over  the  filling  material 
but  with  poor  results  as  the  blocks  give  way  in  fire  and  let  the  filling 
fall  out.  Especial  care  must  be  taken  to  insulate  all  steel  I-beams 
and  other  structural  metal  parts  in  fireproof  structures,  as  the  high 
conducting  power  of  the  metal  will  work  havoc  with  insulation  other- 
wise well  constructed  when  these  beams  and  columns  are  neglected. 
This  and  the  other  difficulties  met  in  fireproof  structures  make  the 
insulation  of  such  buildings  much  more  expensive  than  for  ordinary 
structures  and  it  is  not  generally  believed  that  this  expense  is  justified, 
except  in  special  cases,  as  where  furs  and  valuable  garments  are 
carried  in  store.  Other  goods  generally  carried  are  not  inflammable 


REFRIGERATION  191 

and  most  fires  originate  outside  of  the  storage  rooms  or  on  account 
of  improper  electric  wiring. 

METHODS  OF  COOLING 

In  olden  days,  natural  ice  was  the  sole  reliance  of  cold  storage 
people  and  knowledge  of  the  laws  governing  air  circulation  and  ven- 
tilation was  so  meager  that  little  success  was  had  in  using  it.  Me- 
chanical refrigeration  has  now  become  so  wrell  understood  in  its  pro- 
duction and  application  that  there  is  little  use  for  ice,  even  in  northern 
climes  where  it  is  produced  naturally,  as  the  expense  of  harvesting 
taken  with  that  of  delivery  is  greater  in  many  cases  than  the  cost  of 
making  artificial  ice  and  delivering  it  to  the  customer.  This,  taken 
with  the  fact  that  refrigeration  by  ice  is  very  inefficient  and  expensive 
as  compared  with  the  direct  application  of  cold  produced  mechanic- 
ally, places  ice  out  of  consideration  as  a  cooling  medium,  except 
for  household  refrigerators.  Even  in  this  application  ice  is  being 
abandoned  in  some  quarters,  where  owners  are  able  to  install  one  of 
the  small  automatic  refrigerating  outfits  already  mentioned. 

For  applying  mechanically  produced  refrigeration,  there  are  a 
number  of  methods  in  use,  some  of  which  are  now  considered  obso- 
lete, while  each  of  the  others  has  its  advantages  and  disadvantages. 
In  primitive  cold  stores,  gravity  air  circulation  was  relied  upon  for 
mixing  and  cooling  the  air  to  uniform  temperature  throughout  the 
rooms;  but  the  system  proved  inefficient,  as  most  of  the  cooling  was 
done  by  direct  radiation  and  little  or  no  circulation  of  air  was  induced. 
The  unsatisfactory  results  had  thus  led  to  a  study  of  direct  radiation. 
In  the  first  cold  stores,  pipes  containing  expanding  ammonia  gas  or 
cold  brine  were  placed  directly  in  the  rooms  and  the  cooling  produced 
was  by  direct  radiation  of  heat  from  the  air  in  the  rooms  to  these  pipes. 
As  the  results  were  poor,  various  systems  were  devised  to  improve 
the  circulation;  thus  leading  to  the  indirect-radiation  system,  where 
the  coils  are  located  in  a  loft  separate  and  apart  from  the  room  and 
above  it  to  one  side,  so  that  the  greater  height  gives  a  greater  differ- 
ence in  density  between  the  cold  and  hot  air.  The  circulation  is 
directed  as  desired  by  false  ceiling  and  wall  shields. 

Modern  practice  considers  both  these  radiation  systems  out  of 
date,  the  principal  objection  to  the  indirect  system  aside  from  the 
fact  that  circulation  is  imperfect,  being  the  impracticability  of  intro- 


192 


REFRIGERATION 


ducing  fresh  air  into  the  rooms.  There  are  in  use  at  the  present 
time  five  systems  of  cooling  rooms,  some  of  which  are  combinations 
of  the  elementary  processes.  Thus  we  have  direct  expansion  where 
the  refrigerant  is  expanded  direct  in  the  coils  placed  in  the  rooms  to  be 
cooled,  the  best  arrangement  being  that  with  deflecting  shields,  etc., 
for  directing  circulation  of  the  air  in  the  manner  just  mentioned. 
This  method  can  be  applied  successfully  in  large  rooms  where  the 
temperature  and  duty  to  be  performed  is  constant,  such  as  in  brew- 
eries, packing  houses,  and  large  cold  storage  rooms;  or  where  very 


Fig.  82.    Direct-Expansion  Cold  Store. 

low  temperatures  are  required  as  in  sharp  freezers  for  fish,  poultry, 
etc.,  in  which  work  direct  expansion  is  desirable,  the  efficiency 
being  much  greater  with  this  system  than  with  any  other.  Fig.  82 
illustrates  a  large  room  arranged  for  direct  expansion,  where  the 
ammonia  is  expanded  by  the  valve  A  into  the  piping  B,  the  gas  be- 
ing returned  to  the  compressor  through  the  pipe  C.  Fig.  83  shows 
a  fish  freezing  room  on  each  side  of  which  is  arranged  a  series  of  pipe- 
coil  shelves  through  which  the  ammonia  is  evaporated.  Fish  are 
'aid  in  tin  trays  and  placed  on  the  pipe  shelves  until  the  room  is 


REFRIGERATION 


193 


filled,  when  the  room  is  closed  and  the  ammonia  turned  on  the  coils 
as  long  as  necessary  to  freeze  up  the  fish.  As  the  coils  are  both  above 
and  below  the  trays  and  close  together,  the  application  of  cold  is 
effective  and  only  a  few  hours  are  required  for  freezing. 

In  some  cases,  as  has  already  been  mentioned,  it  is  desirable 
to  use  brine  circulation  for  cooling  the  rooms,  the  arrangement  for 
which  is  shown  in  diagrammatic  form  by  Fig.  84,  which  illustrates 
a  system  using  a  brine-cooling  tank  with  the  brine  coils  set  directly 
in  the  room  to  be  cooled.  This,  it  will  be  seen,  is  an  application  of 
direct  radiation.  The  system  may  be  used  to  better  advantage  with 


Pig.  83.    Fish  Freezing  Room. 

a  brine  cooler  connected  instead  of  the  brine-cooling  tank,  as  the 
cooling  with  double-pipe  brine  coolers  is  more  rapid  and  efficient 
than  with  the  tank,  for  reasons  already  stated.  Fig.  85  illustrates 
a  forced-air  circulation  system,  using  direct-expansion  coils  in  the 
bunker  room,  which  arrangement  is  the  most  modern  practice.  Some 
engineers,  usually  of  the  old-time  stamp,  prefer  to  use  brine  coils  in 
the  bunker  room;  but  there  is  no  advantage  in  this,  as  a  pump  and 
brine  cooler  must  be  employed  for  handling  the  brine.  Cooling  is 
more  effective  with  the  direct-expansion  coils  in  the  bunker  room. 
Some  years  ago  when  manufacturers  were  not  able  to  put  up  pipe 
work  for  direct  expansion,  there  may  have  been  excuse  for  the  brine- 
circulation  system  with  direct  radiation,  but  it  is  now  altogether  out 


194 


REFRIGERATION 


of  date  except  for  those  who  may  be  wedded  to  "their  system"  to 
such  an  extent  that  they  cannot  see  the  light  of  advancement  and 
progress. 

If  for  any  reason  it  is  desired  to  use  brine,  much  more  effective 
cooling  can  be  had  by  passing  the  brine  down  through  the  open  space 
of  the  bunker  room,  after  coming  from  the  cooler,  in  thin  sheets 
flowing  over  vertical  walls  or  with  other  suitable  arrangement.  The 
air  is  forced  through  the  brine  and  cooled  after  which  it  may  be  passed 
to  the  storage  rooms.  By  this  process,  the  brine  purifies  the  air  so 

hat  the  stores  are  kept 
sweet  at  all  times,  the 
gases  and  impurities 
taken  up  from  the  prod- 
ucts in  the  rooms  being 
absorbed  by  the  brine. 
This  system  has  been 
applied  with  consider- 
able success  and  about 
the  only  objection  is 
the  possibility  of  getting 
too  much  moisture  in 
the  air  going  to  the 
rooms ;  which  cannot  oc- 
cur, however,  if  due  re- 
gard is  given  to  the  tem- 
perature used  in  the 
bunker  room,  so  that 
the  air  leaves  at  about  the  temperature  of  the  store  rooms. 

Where  pipe  coils  are  used  in  the  bunker  room,  calcium  chloride 
can  be  used  to  advantage.  It  is  placed  in  trays  over  the  coils  in  such 
a  manner  that  moisture  in  the  air  will  be  taken  up  by  the  calcium, 
forming  brine  that  drips  down  over  the  pipes  and  absorbs  impurities. 
In  any  system  of  cooling,  it  is  important  that  the  air  be  circulated 
so  as  to  maintain  uniform  temperatures  in  all  parts  of  the  various 
rooms.  Also  the  air  must  be  purified  or  renewed  at  suitable  inter- 
vals if  the  goods  are  to  be  kept  in  first-class  condition.  There  is 
much  difference  of  opinion  as  to  how  often  the  air  should  be  changed 
and  the  cold-storage  man  must  use  considerable  judgment  in  this 


Diagram  of  Brine  Circulation  Plant. 


REFRIGERATION 


195 


matter,  as  much  depends  on  the  character  of  the  goods  and  the 
length  of  time  they  have  been  in  store.  Fresh  meats  and  vegetable 
products  when  first  put  in  store,  give  off  a  large  amount  of  gases  and 
impurities  which  must  be  removed,  but  after  having  been  in  store 
for  some  time  there  is  less  of  this  action  tending  to  contaminate  the 
air.  Ordinarily,  if  the  entire  volume  of  air  in  a  room  is  renewed 
with  pure  fresh  air  once  or  twice  a  week,  good  results  will  be  had. 
To  effect  this  in  a  proper  manner  it  is  essential  that  some  system  of 


Fig.  85.    Diagram  of  Air-Circulation  Plant. 

forced-air  circulation  be  employed;  and  in  fact  such  a  system  is 
necessary,  aside  from  the  question  of  ventilation,  if  proper  circulation 
is  to  be  had. 

Although  many  cold-storage  men  are  bitterly  opposed  to  forced- 
air  circulation,  it  is  generally  recognized  by  eminent  authorities  that 
such  circulation  is  necessary  if  good  results  are  to  be  obtained.  There 
is  a  choice  between  the  exhaust  and  pressure  systems  but  the  latter 
is  so  far  superior  that  little  consideration  need  be  paid  to  the  exhaust 
system  of  ventilating  by  drawing  air  out  of  the  rooms.  Compara- 
tively little  power  is  required  for  the  air  circulation  and  the  results 
obtained  where  the  forced-air  system  is  properly  installed  are  much 


196  REFRIGERATION 

superior  to  the  results  with  systems  now  becoming  obsolete. 
This  does  not  mean  that  small  fans  of  the  type  used  in  offices  and 
hotel  parlors  should  be  employed,  as  little  advantage  can  attach  to 
the  use  of  such  apparatus.  A  properly  designed  fan  made  of  light 
weight,  corresponding  to  the  low  speed  and  duty  required  for  the 
slow  circulation  of  air  used  in  refrigerating  rooms,  should  be  used 
and  the  air  should  be  forced  through  bunker  cooling  rooms  in  the 
manner  just  described,  fresh,  purified  air  being  drawn  in  as  necessary. 

In  northern  climates,  it  has  sometimes  been  the  practice  to  ven- 
tilate the  rooms  in  fall  and  winter  by  opening  windows  and  doors, 
but  there  is  some  question  as  to  the  advisability  of  this  practice 
and  it  should  be  applied  with  the  greatest  judgment  and  caution. 
Where  the  outside  temperature  is  about  the  same  as  that  carried  in 
the  rooms  on  a  bright  clear  day,  or,  better  still,  on  a  clear  cold  night, 
there  can  be  no  harm  in  filling  the  rooms  with  Nature's  pure  air. 
There  should,  however,  be  no  guess  work  about  the  matter,  and 
measurement  of  the  moisture  in  the  air  and  its  temperature  should 
be  made  carefully  before  "opening  up."  Where  the  forced-air 
circulation  system  is  used  and  arrangements  made  to  draw  in  fresh 
air  as  needed,  there  is  little  need  for  opening  doors  and  windows  and  in 
fact,  such  openings  should  not  be  used  in  storage  plants  where  pos- 
sible to  avoid  them,  owing  to  the  difficulty  of  insulating  them  and  the 
fact  that  all  necessary  light  can  be  had  more  cheaply  by  using  in- 
candescent electric  lamps.  There  is  no  objection  to  these  lamps  other 
than  the  heat  cast  off  into  the  rooms  and  this  is  small  indeed  com- 
pared to  the  heat  coming  through  the  best  insulated  windows,  even 
where  four  or  five  thicknesses  of  glass  and  air  spaces  are  employed. 

Some  of  the  most  successful  cold-storage  houses  abroad  have  no 
openings  or  doors  in  the  walls,  entrance  being  had  only  through  the 
top  of  the  building.  In  such  cases,  hoists  are  used  to  elevate  the 
goods  to  the  top  and  lower  them  inside  the  building.  In  the  large 
storage  houses  of  receiving  ports  in  England,  where  cargoes  of  fresh 
meats  are  received  from  steamers,  houses  built  on  this  closed  plan 
have  been  most  successful.  Where  a  general  line  of  goods  is  carried, 
as  for  example,  in  the  wholesale  commission  trade,  it  is  imprac- 
ticable to  operate  such  a  house,  as  a  certain  number  of  doors  must 
be  had.  Such  doors  should  be  of  the  best  possible  construction 
and  it  is  usually  better  to  buy  one  of  the  patent  doors  on  the  market. 


REFRIGERATION  197 

The  manufacturers,  being  specialists  in  this  line  of  work,  may  be  con- 
sidered more  competent  to  turn  out  a  good  door  than  any  ordinary 
carpenter  who  may  be  on  a  construction  job.  In  nine  cases  out  of 
ten  the  so-called  "home-made"  doors  constructed  on  the  premises 
will  give  poor  results  and  be  a  constant  source  of  annoyance,  owing 
to  sticking  and  failure  to  open. 

REFRIGERATION  REQUIRED 

The  refrigeration  required  depends  altogether  on  the  effective- 
ness of  the  insulation,  on  the  character  of  the  goods  carried,  on  the 
size  and  shape  of  the  rooms,  the  quantity  of  goods,  and  the  frequency 
with  which  goods  are  taken  in  and  out  of  store.  The  amount  requir- 
ed also  depends  to  some  extent  on  the  temperature  of  the  goods  re- 
ceived and  to  a  much  greater  extent  on  the  temperature  at  which 
the  rooms  must  be  kept.  When  all  these  conditions  are  known, 
Levey  gives  the  following  instructions  for  finding  the  amount  of  re- 
frigeration necessary: 

1.  For  the  room, 

Calculate  the  exact  area  of  the  exposed  surface  in  the  walls,  floor,  and 
ceiling  of  the  rooms  in  square  feet,  and  multiply  the  total  number  of  square 
feet  by  the  numbers  given  opposite  the  required  temperature  and  divide  by 
284,000. 

For  rooms  containing  less  than  1,000  cubic  feet; 

If  held  at  zero  F.  multiply  the  exposed  surface  by  1,775 


5  deg. 
10  " 
20  " 
32  " 
36  " 


710 
535 
355 
265 
180 


For  rooms  containing  1,000  to  10,000  cubic  feet; 

If  held  at  zero  F.  multiply  the  exposed  surface  by  1,250 

"     "       5  deg.  "          "           "         «  "  "  600 

"     "     10     "     "         "           "         "  "  "  300 

"     "     20     "     "         "           "         "  "  "  190 

n     f     32     a     «         a           a         a  a  160 

"     "     36     "     "         "           "         "  "  "  125 
For  rooms  containing  over  10,000  cubic  feet; 

If  held  at  zero  F.  multiply  the  exposed  surface  by  1,100 

"     "       5  deg.  "         "           "         "  "  "  550 

a     a     10     a     a         it           K         a  a  «  275 

it         It         2Q          II         I,                 tl                     „                  „  «  U  jgQ 

"     "     32     "     "         "           "         "  "  "  140 

"     "     36     "     "         "           "         "  "  "  110 


198  REFRIGERATION 

2.  For  the  stores. 

Multiply  the  amount  of  goods  (in  pounds)  to  be  stored  per  day  by 
the  number  of  degrees  the  temperature  is  to  be  lowered  and  by  the  specific 
heat  of  the  goods,  and  divide  by  284,000.  This  will  give  the  amount  of  refrig- 
eration in  tons  per  day  necessary  to  hold  the  goods  at  the  required  temperature. 

Add  together  the  results  of  1  and  2  and  the  total  will  be  the  amount 
of  refrigeration  in  tons  per  day  which  will  be  required  to  hold  the  goods  and 
the  room.  If  the  goods  are  to  be  frozen,  the  latent  heat  of  freezing  should 
be  added  to  the  heat  to  be  removed  in  lowering  the  temperature. 

COLD  STORAGE 

Handling  Goods.  The  proper  handling  of  products  stored  is  a 
matter  of  great  importance,  both  from  the  standpoint  of  preservation 
and  profit.  If  goods  are  carelessly  piled  in  a  room  so  that  there  can 
be  little  circulation  of  air  among  the  packages,  deterioration  is  the 
result,  particularly  with  those  packages  in  the  middle  of  the  pile. 
Also  there  is  much  danger  of  crushing  goods  in  the  lower  tiers,  where 
a  number  of  cases  or  barrels  are  packed  one  on  top  of  the  other. 
Thus,  for  example,  in  storing  apples  in  barrels  several  tiers  high, 
2  x  4-inch  scantling  should  be  placed  on  the  floor  under  the  ends  of 
the  first  tier  and  similar  scantlings  should  be  placed  on  the  barrels  be- 
fore laying  on  each  successive  tier.  In  this  way,  the  weight  is  taken 
on  the  heads  of  the  barrels  and  not  on  the  bilge,  and  danger  of 
crushing  the  fruit  in  the  lower  tiers  is  thereby  eliminated. 

It  is  important,  of  course,  to  give  attention  to  handling  the  goods 
in  and  out  of  store  with  as  much  facility  as  possible,  thereby  saving 
time  and  trouble,  but  as  these  matters  are  usually  looked  after  by 
warehouse  foremen  who  do  not  wish  to  do  any  work  that  they  can 
avoid,  it  is  not  generally  up  to  the  manager  to  be  on  the  lookout  in 
this  particular.  Some  classes  of  goods  can  be  stored  more  compactly 
than  others.  It  matters  little  how  close  cases  of  butter  are  piled; 
but  articles  that  give  off  moisture,  such  as  fruits,  should  not  be  piled 
too  close  and  with  too  many  packages  in  a  pile.  With  other  classes 
of  goods,  as  frozen  fish  and  poultry,  for  example,  the  more  compact 
the  goods  can  be  stored  the  better,  as  close  packing  tends  to  check 
the  drying  and  evaporating  action  of  the  air  in  removing  the  coating 
of  ice  used  to  prevent  drying  out. 

In  taking  goods  from  store,  there  is  likely  to  be  trouble  from 
sweating,  as  the  low  temperature  of  the  goods  condenses  moisture 
present  in  the  atmosphere.  This  may  have  a  decidedly  detrimental 


REFRIGERATION  199 

effect  with  some  classes  of  goods,  as  eggs  and  fruits,  so^hat  precau- 
tions should  be  taken  to  prevent  the  action  by  cooling  the  goods 
gradually.  This  may  be  done  by  piling  them  in  the  receiving  room 
with  a  heavy  wagon  tarpaulin  or  other  similar  covering  placed  over 
the  pile.  In  fall  weather,  if  the  goods  are  removed  in  this  way  at 
night  they  will  be  all  right  by  the  next  morning,  but  in  the 
summer  season  where  goods  are  taken  out  of  store  at  low  temper- 
atures, as  much  as  36  to  48  hours  may  be  necessary  to  get  them 
warmed  up  properly.  On  the  other  hand  goods  taken  into  storage 
can  be  handled  much  better  both  from  the  standpoint  of  econ- 
omy and  preservation  of  quality  by  lowering  the  temperature  grad- 
ually. 

In  all  mechanical  and  engineering  lines,  it  is  a  well-recognized 
fact  that  sudden  changes  of  conditions  are  effected  at  comparatively 
high  cost.  This  is  particularly  true  of  refrigerating  work,  where 
sudden  temperature  reductions  cost  much  more  than  the  same  re- 
duction effected  gradually.  In  storing  butter,  which  is  usually  kept 
at  about  zero  F.,  it  is  highly  advisable  to  place  the  trucks  in  a  com- 
paratively warm  room  before  taking  them  into  the  sharp  freezers. 
When  this  is  done,  much  less  cooling  surface  need  be  used  for  the 
freezers  and  the  results  are  more  economical  and  satisfactory  in  every 
way.  There  are  many  other  points  in  handling  goods  in  cold  stores 
that  cannot  be  taken  up  in  brief  space,  but  it  should  be  pointed  out 
that  the  large  number  of  failures  in  small  storage  plants,  usually 
operated  in  connection  with  ice  plants,  is  due  mostly  to  the  fact  that 
several  products  are  stored  in  the  same  room  at  a  common  tempera- 
ture which  makes  impossible  good  results,  so  necessary  to  permanent 
success  in  storage  work. 

Where  goods  are  to  be  stored  for  any  length  of  time,  there  are  few 
different  products  that  can  be  stored  in  the  same  room  to  advantage. 
Thus  butter  requires  a  lower  temperature  than  chesee,  while  fruits 
are  kept  at  a  higher  temperature  than  the  cheese.  If  eggs  and  butter 
are  kept  in  the  same  storage  room  with  other  materials,  they  will  soon 
absorb  the  flavor  of  the  fruits  and  other  things  in  the  room.  Oranges, 
pineapples,  etc.,  may  have  the  most  delicious  flavors,  but  these  may 
not  be  very  agreeable  to  the  palate  in  butter  or  cheese.  Such  prod- 
ucts may  be  stored  together  for  a  short  time  with  some  success  if 
great  care  is  taken  with  the  ventilation,  but  it  is  the  practice  of  all 


200 


REFRIGERATION 


TABLE  .XXIII 
Rates  for  Cold  Storage 


GOODS  AND  QUANTITY 

FIRST 
MONTH 

EACH 
SUCCEEDING 
MONTH 

IN  LARGE 

QUANTITIES, 
PER  MONTH 

SEASON  RATE 
PER  BBL. 
OR  100  LBS. 

II 

£* 

Apples,  per  bbl  
Bananas,  per  bunch  .  .  

$0.15 
15 

$0  .  12*. 
10 

$0.12*. 

10  " 

$0.45 

May  1 

Beef,  mutton,  pork,  and  fresh  meats, 
per  Ib  

.00| 

.00* 

•OOf 

Beer  and  ale,  per  bbl  

.25 

.2   " 

Beer  and  ale,  per  *  bbl  

.15 

.1 

Beer  and  ale,  per  i  or  i  bbl  
Beer,  bottled,  per  case  
Beer,  bottled,  per  bbl  

.10 
.10 
.20 

.1 
.1. 

.2. 



Berries,  fresh,  of  all  kinds,  per  qt.  .'.  . 
Berries,  fresh,  of  all  kinds,  per  stand. 
Butter  and  butterine,  per  Ib  
(See  also  butter  freezing  rates.) 
Buckwheat  flour,  per  bbl  
Cabbage,  per  bbl  
Cabbage,  per  crate  

.00* 

.10" 
.OOi 

.15 
.25 
.10 

.OOi 
"'.OOi' 

.10* 
.20 
.18 

.OOi 

"'.ooi' 

.10 
.20 
.08 

.50-75 
.50 

Jan.   1 
Oct.  1 

Calves  (per  day),  each  

.10 

Calves,  per  Ib  

.00| 

.00* 

.OOf 

Canned  and  bottled  goods,  per  Ib.  .  . 
Celery  per  case 

.OOi 
15 

.OOi 
10 

.OOi 
10 

Cheese  per  Ib 

OOJ 

OOi 

OOi 

50     60 

Jan    1 

Cherries  per  quart 

00* 

00* 

OOi 

Cider,  per  bbl  

.25" 

15* 

15 

Cigars,  per  Ib  

.OOi 
25 

.OOi 
20 

•  OOi 
15 

Cranberries,  per  case  
Corn  meal,  per  bbl  
Dried  and  boneless  fish,  etc.,  per  Ib. 
Dried  corn,  per  bbl  
Dried  and  evaporated  apples,  per  Ib  . 
Dried  fruit,  per  Ib  
Eggs,  per  case  
Figs  per  Ib 

.10 
.15 
•  OOi 
.124 

.OOi 
.OOi 
.15 
OOi 

.'12*' 
•  OOi 
.10 
.00  A 
.OOi 
.12* 
OOi 

"'id' 

.00  J 

.10 

.66i' 

.10 
00TV 

'".50" 

"  .50 
40-  .50 
50-  .60 

Nov.   i 

Nov.   i 
Nov.   1 
Jan.  1 

Fish  per  bbl 

20 

18 

15 

75 

Oct    1 

15 

13 

12* 

50 

Oct    1 

(See  also  fish  freezing  rates.) 
Fruil  s   fresh    per  bbl 

25 

20 

20 

Fruits,  fresh,  per  crate  

.10 

.08 

.08 

Furs,  undressed,  hydraulic  pressed, 
per  Ib  

.00* 

.OOi 

.001 

1  00 

Oct   1 

Furs,  dressed,  per  Ib  
Ginger  ale,  bottled,  per  bbl  
Grapes,  per  Ib  
Grapes,  per  basket  
Grapes,  Malaga,  etc.,  per  keg  
Hops  per  Ib  .  

.03 
.20 
.00* 
.03 
.15 
OOi 

.02* 
.15" 
.OOi 
.02 
.124 
OOi 

f   "02l 
...15 
.OOi 
.01 
.12} 
OOi 

8.00 

'  2  66 

Oct.  1 
May  V 

Lard  per  tierce  .  ... 

25 

20 

20 

1  00 

Nov    1 

Lard  oil,  per  cask  
Lemons,  per  box  
Macaroni,  per  bbl  
Maple  sugar,  per  Ib  

.25 
.15 
.20 
-00i 

.20 
.12* 
.15" 
".OOi 

.20 
.10 

..m 

-OOi 

1.00 
.50 

:^'a 

Nov.  1 
Nov.  1 

Nov'.'l 

REFRIGERATION 


201 


TABLE  XXIII— Continued 
Rates  for  Cold  Storage 


1! 
•S| 

EACH 

SUCCEEDING 
MONTH 

IN  LARGE 

QUANTITIES, 
PER  MONTH 

SEASON  RATE 
PER  BBL. 
OR  100  LBS. 

SEASON 

ENDS 

Maple  syrup,  per  gallon  
Meats,  fresh,  per  Ib  
Nuts,  of  all  kinds,  per  Ib  
Oatmeal,  per  bbl  
Oil,  per  cask  
Oil,  per  hogshead  
Oleomargarine,  per  Ib  
Onions,  per  bbl  
Onions,  per  box  
Oranges,  per  box  
Oysters,  in  tubs,  per  gal  
Oysters,  in  shell,  per  bbl  
Peaches,  per  basket  

.01* 
.OOf 

.001 

.20 
.25 
1.00 
.00* 
.15 
.12* 
.15" 
.05 

.r,o 

.10 
.20 
.40 
•  00* 
.20 
.25 

.001 

.25 
.20 
.25 
.15 
.30 
.00?, 
.25 
.15 
.25 
.10 

.OH 

.00* 
•OOi 
.15 
.20 
.80 
.00 
.12i 

.10* 

.12* 
.04 
.40 
.08 
.15 
.30 

:8» 

.20 

.001 

.20 
.15 
.20 

.m 

.25" 
.001 
.20 
.10 
.25 
,10 

.01 
.OOf 
•00£ 
.12* 

"'66i' 
.10 

.40-.  50 

.'56-!  60 
.50 

Nov.  i 

May  Y  ' 
Nov.'  1  ' 

Jani  1 
May  1 
May  1 
Nov.l 

Nov.'l  ' 
6'c't!  1 

.10 

'    .30 

.07 

"'.ooi' 

.15 
.20 
.00 
.20* 

.m 

.15" 
.10 
.20 
.00  J 

.15 
.08 

2.00 
.60 
1.20 
1.00 

.'GO-  '.75 

1.00 

Pears,  per  box  
Pears,  per  bbl  

Pigs'  feet,  per  Ib  
Pork,  per  tierce  

Potatoes,  per  bbl  
Preserves,  jellies,  jams,  etc.,  per  Ib  .  . 
Provisions,  per  bbl  
Rice  flour,  per  bbl  .  ,  
Sauerkraut,  per  cask  
Sauerkraut,  per  *  bbl  
Syrup,  per  bbl  
Tobacco,  per  Ib  
Vegetables,  fresh,  per  bbl  
Vegetables,  fresh,  per  case  
Wine,  in  wood,  per  bbl  
Wine,  in  bottles,  per  case  



large  storage  establishments  to  have  separate  rooms  and  spaces  for 
the  different  classes  of  goods  stored. 

Storage  Rates.  All  storage  business  is  conducted  for  revenue 
and  it  is  important  that  such  a  schedule  of  rates  be  adopted  as  will 
allow  a  reasonable  profit  for  the  capital,  skill,  and  experience  neces- 
sary to  run  a  cold  storage  establishment.  Rates  vary  with  local 
circumstances,  conditions,  and  with  the  products  stored  and  the 
time  they  are  kept  in  storage,  so  that  no  general  rule  can  be  laid  down. 
Capacity  for  storage  and  the  demand  therefor  as  well  as  the  competi- 
tion to  be  met  must  all  be  considered.  As  a  rough  guide,  Siebel  gives 
the  data  presented  in  Table  23,  the  figures  being  averages  of  rates 
prevailing  in  a  number  of  large  cold-storage  establishments. 


202  REFRIGERATION 

APPLICATIONS  OF  REFRIGERATION 

Breweries.  Two  of  the  most  important  uses  of  refrigeration 
in  ice-making  and  cold-storage  work  have  already  been  taken  up  at 
considerable  length,  but  these  industries,  important  as  they  are,  do 
not  cover  the  field  of  refrigeration  applications  by  any  means.  After 
ice  and  cold-storage  plants,  the  brewery  industry  is  about  the  most 
important  application  of  refrigeration.  In  making  beer  there  are 
three  distinct  operations,  the  first  being  the  preparation  of  malt  from 
barley,  the  second  the  preparation  of  the  wort  from  malt,  and  finally 
the  fermentation  of  wort  to  convert  it  into  beer.  Specially  prepared 
malt  is  washed  or  diluted  with  hot  water  to  form  clear  wort  which  is 
boiled  with  hops  to  make  the  beer  wort.  The  wort  thus  made  is 
cooled  and  converted  into  beer  by  adding  yeast,  which  brings  about 
decomposition  or  fermentation,  the  process  taking  place  in  large 
vessels  placed  in  rooms  cooled  by  refrigeration.  The  density  of 
wort  is  determined  by  a  special  instrument  known  as  the  Balling 
saccharometer,  which  is  so  graduated  that  when  immersed  in  the 
liquid  it  indicates  the  percentage  of  solid  matter — mostly  dextrine 
and  saccharine — that  the  wort  contains.  The  specific  gravity  and 
the  specific  heat  of  wort  may  be  taken  from  standard  tables,  and  with 
this  data  the  refrigeration  required  can  be  figured  by  the  methods 
already  explained. 

Cooling  wort  makes  up  the  greatest  part  of  the  refrigerating 
work  to  be  done  in  a  brewery,  but  aside  from  this  the  machinery  must 
remove  the  heat  of  fermentation  and  keep  the  temperature  of  the 
cellars,  fermenting  rooms,  etc.  at  34°  to  38°  F.  As  this  is  about  the 
lowest  temperature  required,  it  is  seen  that  brewery  work  is  com- 
paratively light,  but  owing  to  the  fact  that  the  hot  wort  must  be  cooled 
quickly,  it  is  necessary  to  install  larger  machines  in  breweries  than 
would  otherwise  be  called  for. 

Packing  Houses.  Packing  houses  employ  artificial  refrigera- 
tion to  a  large  extent  and  it  is  safe  to  say  that  this  industry  as  it  exists 
to-day  would  be  impossible  without  artificial  methods  of  cooling.  There 
are  three  temperatures  used  respectively  in  the  chill  room,  holding 
room,  and  freezing  room.  After  the  carcasses  are  dressed,  it  is  impor- 
tant to  get  rid  of  the  animal  heat  as  rapidly  as  possible.  This  is  done 
by  suspending  the  carcasses  in  the  chill  room  which  carries  a  tempera- 
ture of  about  28  degrees.  Ample  ventilation  is  provided  in  this  room 


REFRIGERATION  203 

to  remove  the  gases  and  impurities  given  off  from  the  meat  in  cooling. 
When  the  temperature  has  been  reduced  from  blood  heat — about 
95  degrees — to  35  degrees,  the  meat  is  removed  to  the  holding  room, 
in  which  the  temperature  ranges  from  32  to  35  degrees,  but  never 
low  enough  to  freeze  the  meat.  The  temperature  of  the  freezing 
room  may  be  10  degrees  or  under,  but  in  freezing  meat,  it  is  neces- 
sary that  the  cooling  be  done  gradually. 

If  possible  to  avoid  it,  meat  is  never  frozen;  but  if  it  must  be 
shipped  long  distances,  requiring  several  days  in  transit,  freezing  is 
necessary.  Ample  time  should  be  allowed  for  the  process,  the  tem- 
perature being  reduced  gradually,  as  otherwise,  the  meat  will  be 
seriously  damaged.  If  the  temperature  is  reduced  suddenly,  the 
outer  portion  of  the  meat  is  frozen  solid  before  the  temperature  inside 
can  be  lowered  and  the  contraction  of  the  outer  layer  of  frozen  meat 
on  the  inner  part  causes  rupture  of  the  congealed  cells  in  the  meat  so 
that,  when  finally  thawed  out,  it  is  found  that  the  quality  of  the  carcass 
has  deteriorated.  In  cutting  into  a  joint  of  meat  so  treated  the  flesh 
near  the  bone  will  be  found  to  be  of  a  pulpy  consistency.  Aside  from 
this  damage  to  the  meat,  it  costs  more  to  do  the  freezing  where  the 
temperature  is  reduced  rapidly,  not  only  on  account  of  the  fact  that 
sudden  changes  are  always  costly,  but  more  particularly  by  reason  of 
the  outer  layer  of  frozen  meat  having  insulating  qualities. 

So-called  bone  stink  is  nothing  more  than  decaying  marrow, 
which  is  due  in  most  cases  to  rapid  freezing  but  may  be  due  in  some 
measure  to  the  condition  of  the  animal  before  killing.  Frozen  meat 
may  be  kept  for  several  months  at  a  temperature  of  31  degrees,  but 
care  should  be  taken  not  to  let  the  temperature  rise  above  this  figure, 
for  a  rise  even  to  33  degrees  may  result  in  the  meat  spoiling  in  less 
than  a  month,  although  if  the  ventilation  is  good  and  other  conditions 
favorable  it  may  be  kept  as  long  as  two  months.  Usually  frozen 
meat  is  kept  about  six  months  with  perfect  safety.  If  care  is  taken 
in  thawing  out,  the  meat  will  be  palatable  and  wholesome.  In  dis- 
cussing cold  storage,  the  importance  of  circulation  and  ventilation 
was  mentioned  and  the  point  applies  with  particular  force  to  pack- 
ing-house work,  as  meat  is  sensitive  to  improper  conditions  and  white 
mold  spots  are  readily  formed  under  such  circumstances. 

Creameries.  Creameries  are  in  late  years  becoming  large  users 
of  refrigeration,  as  it  is  found  almost  impossible  to  turn  out  good 


204  REFRIGERATION 

dairy  products  without  artificial  cooling.  From  the  time  the  milk 
comes  from  the  animals  until  it  is  worked  up  into  butter,  cheese,  and 
other  products,  its  temperature  should  be  regulated  carefully.  Like 
breweries,  creameries  require  light  or  moderate-temperature  refrigera- 
tion, there  being  two  objects  in  using  refrigeration  in  the  industry — • 
the  first,  control  of  bacteria  life  in  the  milk;  the  second,  regulation  of 
temperature  as  required  in  separating  the  cream  from  the  milk  and 
in  churning  it.  It  is  desirable,  though  not  always  possible,  that  the 
animal  heat  of  the  milk  coming  from  the  cows  should  be  removed  at 
once  and  if  this  can  be  done  the  quality  is  much  improved.  As  a 
rule,  however,  the  milk  delivered  to  creameries  by  farmers  has  a  tem- 
perature of  from  65  to  70  degrees  in  summer  and  from  40  to  50  de- 
grees in  the  winter.  This  milk,  on  coming  to  the  creamery,  should 
be  pasteurized  by  being  heated  up  in  a  special  apparatus  to  a  tem- 
perature of  about  180°  F.,  thereby  destroying  bacteria.  Not  all  the 
bacteria  life  is  destroyed  at  this  temperature  but  the  milk  is  made 
immune  for  all  practical  purposes  and  the  danger  of  burning  that 
would  be  incurred  at  higher  temperatures  is  avoided. 

In  good  separators,  the  cream  can  be  removed  from  the  milk  at 
any  temperature  above  100  degrees,  but  160  is  the  proper  tempera- 
ture. After  pasteurization  and  separation,  the  milk  is  cooled  down 
by  being  passed  over  a  cooler  of  the  Baudelot  type,  through  which 
well  water  runs,  and  is  returned  to  the  farmers.  The  cream  is  then 
cooled  rapidly  by  being  passed  over  a  circular  capillary  cooler  through 
the  corrugations  of  which  well  water  is  circulated.  On  leaving  this 
cooler  it  has  a  temperature  of  about  70  degrees  and  refrigeration  is 
applied  to  reduce  the  temperature  to  50  degrees,  which  gives  the 
best  results  for  ripening.  In  this  latter  process,  the  temperature  rises 
to  about  70  degrees  and  refrigeration  must  again  be  applied  to  reduce 
this  to  48  degrees,  at  which  temperature  the  cream  goes  to  the  churn. 
Butter  is  kept  in  cold  stores  at  about  zero,  as  already  mentioned. 
Cheese  must  be  made  and  stored  at  moderate  temperatures  if  it  is  to 
ripen  properly.  The  whole  thing  in  creamery  refrigeration  is  to 
control  the  temperatures  exactly  as  desired,  and  this  can  be  done 
only  when  refrigeration  is  used. 

Miscellaneous  Applications.  Aside  from  the  leading  industries 
discussed,  refrigeration  is  used  in  a  number  of  manufacturing  and 
industrial  processes.  0  One  of  the  largest  applications  is  that  for 


REFRIGERATION  205 

drying  air.  A  number  of  manufacturing  processes  require  dry  air, 
one  of  the  most  important  being  blast  furnace  operation.  This  is  a 
comparatively  new  application,  as  until  within  the  last  few  years, 
little  was  known  of  the  extent  to  which  moist  air  causes  loss  in  steel 
mills.  It  has  been  found  that  by  using  a  refrigerating  machine  to 
lower  the  temperature  of  the  air  used  in  blast  furnaces,  thereby  caus- 
ing it  to  reach  the  dew  point  and  precipitate  practically  all  contained 
moisture,  a  great  economy  is  had,  the  air  being  afterwards  reheated 
by  passing  through  gas  stoves  fed  with  waste  gases  coming  from  the 
furnaces.  Sufficient  coal  and  more  is  saved  in  the  blast  furnaces 
than  is  required  to  drive  the  steam  plant  necessary  for  the  refrigera- 
ting machine,  while  at  the  same  time  the  production  of  the  furnace  is 
almost  doubled.  Plants  for  this  work  are  of  large  capacity  ranging 
up  into  the  thousands  of  tons. 

Theaters,  halls,  and  residences  are  now  cooled  by  artificial 
refrigeration  in  summer,  the  process  generally  used  being  a  forced- 
air  circulation  where  the  air  is  driven  through  washing  machines 
which  remove  all  impurities,  and  then  passed  over  cooling  coils  before 
going  into  the  ventilating  ducts.  In  the  case  of  theaters,  the  most 
usual  arrangement  is  to  have  the  ventilating  ducts  pass  under  the 
lloor,  the  openings  from  the  ducts  being  underneath  the  seats  in  all 
parts  of  the  auditorium,  so  that  ventilation  is  uniform  without  drafts 
and  with  the  air  at  suitable  conditions  of  temperature  and  humidity. 

Confectioners  find  use  for  refrigeration  in  maintaining  the  tem- 
perature of  dipping  rooms  so  that  the  candies  are  kept  firm.  Bakers 
likewise  require  cooling  in  their  establishments  to  maintain  constant 
temperature  in  the  mixing  rooms.  Heating  and  cooling  coils  are 
provided  so  that  the  temperature  may  be  raised  or  lowered  as  re- 
quired to  keep  it  at  a  constant  figure.  The  result  of  this  care  is  bread 
of  uniform  texture  from  day  to  day,  so  that  housekeepers  can  depend 
on  getting  the  same  kind  of  bread  each  day.  This  enables  the  pro- 
gressive baker  to  take  trade  from  competitors. 

In  the  sporting  world  also  refrigeration  has  its  uses,  as  all  large 
cities  nowadays  have  their  skating  rinks  in  which  large  ice  surfaces 
are  formed  artificially  for  the  amusement  of  the  public  and  incident- 
ally the  profit  of  the  owners.  In  laboratory  experimental  work  ex- 
tremely low  temperatures  are  frequently  required  and  these  may  be 
had  with  the  refrigerating  machine,  using  special  intensifying  ap- 


206  REFRIGERATION 

paratus.  Medical  men  have  long  appreciated  the  value  of  ice  and 
low  temperatures  in  handling  certain  forms  of  disease.  In  fevers 
especially,  ice  is  almost  a  necessity  if  the  disease  is  to  be  kept  under 
control  This  fact  as  already  mentioned  was  largely  responsible  for 
the  development  of  refrigerating  machinery.  Early  machines  and 
experiments  were  mostly  made  by  physicians  in  the  effort  to  afford 
a  ready  means  of  alleviating  suffering.  This  use  of  the  refrigerating 
machine,  aside  from  all  other  applications,  gives  refrigeration  a  com- 
manding place  among  the  world's  greatest  industries.  If  one  stops 
to  consider,  it  is  seen  that  there  is  scarcely  a  food  product  or  other 
material  having  to  do  with  human  existence  with  which  refrigeration 
does  not  have  to  do  at  some  time  or  other.  Thus  the  importance  of 
refrigeration  as  applied  to-day  becomes  more  apparent.  Certainly 
no  other  scientific  development  has  lent  itself  to  application  in  a  wide 
and  varied  field  of  usefulness  in  a  manner  that  can  compare  in  any 
way  with  mechanical  refrigeration  as  applied  at  the  present  time, 


INDEX 


PAGE 

Absorber 51 

Absorption  system.  ....... 46 

absorber 51 

ammonia  pump 52 

ammonia  regulator 53 

analyzer 48 

binary  systems 56 

care  and  management .' 57 

charging 59 

condenser 50 

economy  of  absorption  machine 61 

efficiency  tests : 60 

equalizer 50 

generator 48 

operation 53 

power  for  absorption  plant 53 

rectifier 50 

Air-machine 2 

Air  system,  arrangement  of 37 

Ammonia 29 

loss  of 142 

Ammonia  condensers 94 

atmospheric  condenser 98 

double-pipe  condenser 104 

oil  separator  or  interceptor 109 

submerged  condenser 95 

Ammonia  liquor t 32 

Ammonia  pump .- 52 

Ammonia  receiver. 125 

Ammonia  regulator 53 

Analyzer 48 

Aqua  ammonia 32 

Atmospheric  condenser 98 

Auxiliary  apparatus 125 

ammonia  receiver 125 

pipes 125 

pressure  gauges 128 

valves 128 

B 

Binary  systems 56 

Brine  agitators 156 

Brine  cooler .  .                  118 


2  INDEX 

PAGE 

Brine  tank 114 

Breweries 202 

C 

Can  plant  equipment. 147 

Can  system 146 

Carbon  dioxide 29 

Charging 134 

Cold,  production  of 20 

Cold-air  machine 36 

arrangement  of  air  system 37 

commercial  form  of  air  machine 38 

compressor  cylinder 41 

Cold  storage 178,  198 

goods,  handling  of 198 

storage  rates 201 

Commercial  form  of  air  machine 38 

Commercial  machines 81 

carbon  dioxide  machines 87 

horizontal  double-acting 81 

Linde 83 

Triumph 81 

small  refrigerating  plants 90 

vertical  compressors 85 

Great  Lakes 86 

York 85 

Compression  system 61 

compressor  piston 73 

compressors 64 

lubrication 78 

operating  principle 62 

stuffing  box 75 

valve  operation f 71 

valve  proportions 72 

water  jacket 76 

Compressor  cylinder 41 

Compressor  losses 93 

Compressors 64 

essentials  in.  . 66 

piston 73 

valves 67 

vertical 85 

Condenser .* 50 

Conduction 20 

Convection : 19 

Cooling,  methods  of 191 

Cooling  coils  and  gas  cooler 152 

Cooling  towers .  109 

Crane  and  hoist. .  .  158 


INDEX  3 
D 

PAGE 

Distilling  apparatus 148 

Double-pipe  condenser 104 

Dumping  and  filling 158 

E 

Equalizer 50 

Evaporators 113 

brine  cooler 118 

brine  tank 114 

Expansion  coils 154 

F 

Filters 152 

Freezing  tank 154 

G 

Generator 48 

Grating  and  covers 156 

H 

Heat 4 

Heat  measurement,  units  of 6 

Hot  skimmer  and  reboiler 149 

I 

Ice,  storing  and  selling 174 

Ice  cans 155 

Ice-making  plants 145 

brine  agitators 156 

can  plant  equipment 147 

can  system : 146 

cooling  coils  and  gas  cooler 152 

crane  and  hoist 158 

distilling  apparatus 148 

dumping  and  filling 158 

expansion  coils 154 

filters 152 

freezing  tank 154 

grating  and  covers •  156 

hot  skimmer  and  reboiler 149 

ice  cans 155 

layout 160 

plate  system 162 

steam  condenser 149 

Ice-plant  insulation 176 

Insulation.  . .                        182 


4  INDEX 

L  PAGE 

Layout.  . 160 

Lubrication 78 

N 

Non-conductors 183 

O 

Oil  separator  or  interceptor 109 

P 

Packing  houses 202 

Pipes.  . 125 

Plant,  operation  and  management  of 139 

ammonia,  loss  of 142 

purging  and  pumping  out  connection 143 

Plant  capacity,  unit  of 13 

Plate  system 162 

Preservation,  conditions  for 179 

Pressure  gauges 128 

R 

Radiation 18 

Rectifier 50 

Refrigerants,  tests  of 33 

Refrigerating  plant,  proportion  between  parts 132 

Refrigerating  plants  (small) 90 

Refrigeration 1-206 

absorption  system 46 

air-machine 2 

ammonia  condensers 94 

applications 202 

breweries 202 

miscellaneous 204 

packing  houses 202 

auxiliary  apparatus 125 

charging 134 

cold,  production  of 20 

cold-air  machine 36 

cold  storage 198 

cold  storage  (general) 178 

cooling,  methods  of 191 

cooling  towers 109 

commercial  machines 81 

compression  system 61 

compressor  losses 93 

conduction. . .           20 


INDEX  5 

Refrigeration  1>AQB 

convection 19 

definitions 3 

heat 4 

heat  measurement,  units  of 6 

historical 1 

ice,  storing  and  selling 174 

ice-making  plants 145 

ice-plant  insulation. 176 

insulation 182 

methods  of 131 

operation  and  management  of  plant 139 

radiation 18 

refrigerants,  tests  of 33 

refrigerating  plant,  proportion  between  parts 132 

required 197 

systems  of 36 

testing % 134 

unit  of  plant  capacity 13 

vacuum  process 44 

S 

Steam  condenser 149 

Storage  rates 201 

Stuffing  box 75 

Submerged  condenser 95 

Sulphur  dioxide 29 

T 

Table 

ammonia,  solubility  of  in  water 32 

aqua  ammonia,  strength  of 34 

beer  wort,  specific  heat  and  specific  gravity  of 13 

calcium  brine  solution,  properties  of 120 

cold  storage,  rates  for 200,  201 

critical  data 24 

freezing  mixtures,  composition  of 21 

gas,  cubic  feet  pumped  per  ton 72 

heat  generated  by  absorbing  ammonia 54 

refrigerants,  comparative  values  of  three 27 

refrigerants,  qualities  of  principal 26 

salt  brine  solution,  properties  of 121 

saturated  ammonia  gas,  properties  of 31 

saturated  carbon  dioxide,  properties  of 30 

saturated  sulphur  dioxide,  properties  of 30 

specific  heat  of  various  susbstances  under  constant  pres- 
sure   12 

substances,  boiling  point  and  latent  heat  of 25 


6  INDEX 

Table  PAOK 

substances,  fusion  and  vaporization  data  of 14 

substances,  non-conducting  power  of 184 

temperatures  for  cold  storage  of  products 181 

thermometer  scales 10 

Tank  insulation 177 

Testing 134 


Vacuum  process 44 

Vacuum  pump 45 

Valve  operation 71 

Valve  proportions 72 

Valves 128 

W 

Water  jacket 76 


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ical, sanitary,  and  steam  engineering,  and  textile  manufacturing. 
It  adapts  its  courses  to  the  needs  of  the  individual,  by  starting  him 
where  his  previous  education  stopped,  and  giving  him  only  such 
work  as  is  necessary  to  fit  him  for  the  work  he  wants  to  do. 

On  request  the  School  will  mail  to  any  address  a  Bulletin 
containing  full  information  regarding  its  courses  and  methods. 
It  employs  no  representative  other  than  its  own  publications. 

AMERICAN  SCHOOL  OF  CORRESPONDENCE 

CHICAGO,  U.  S.  A. 


American  School  of  Correspondence 

PRACTICAL  HANDBOOKS  FOR  HOME  STUDY 


OWING  to  a  constant  and  increasing  demand  for 
low-priced    single    volumes    covering    the    sub- 
jects treated    in    the   courses    and    cyclopedias 
of  the  American  School  of  Correspondence,  a 
series  of  practical  handbooks  have  been  com- 
piled to   be  sold   through  the   Book   Stores  all   over  the 
world.     If  any  purchaser  finds  that  his  local  dealer  does 
not    carry    the   particular   title   which    interests    him,    he 
can    order    direct    from    the    publisher,    who    will    make 
shipment  on  receipt  of  price.      If,  after  five  days'  exam- 
ination, the    volume    is    found  unsuited   to  his   need,   the 
purchaser  may  return  it  and  his  money  will  be  promptly 
refunded. 


Partial  List  of  Titles  and  Authors 


PRICE 


Alternating- Current  Machinery William  Esty $3.00 

Architectural  Drawing  and  Lettering Bourne-von  Hoist-Brown  1.50 

Bank  Bookkeeping ,. Charles  A.  Sweetland 1.00 

Boiler  Accessories ' Walter  S.  Leland 1.00 

Bridge  Engineering — Roof  Trusses Frank  O.  Dufour 3.00 

Building  and  Flying  an  Aeroplane Charles  B.  Hay  ward 1.00 

Building  Superintendence Edward  Nichols 1.50 

Business  Management,  Part  I _ James  B.  Griffith 1.50 

Business  Management,  Part  II Russell-Griffith 1.50 

Carpentry Gilbert  Townsend 1.50 

Care  and  Operation  of  Automobiles Morris  A.  Hall 1.00 

Commercial  Law John  A.  Chamberlain 3.00 

Compressed  Air Lucius  I.  Wightman 1.00 

Contracts  and  Specifications James  C.  Plant 1.00 

Corporation  Accounts  and  the  Voucher  System  ..James  B.  Griffith 1.00 

Cotton  Spinning Charles  C.  Hedrick 3.00 

Department  Store  Accounts Charles  A.  Sweetland  ...  1.50 

Descriptive  Astronomy Forest  Ray  Moulton.-    _  1.50 

Dynamo-Electric  Machinery F.  B.  Crocker.  . .  .1.50 

Electric  Railways Henry  H.  Norris 1.50 

The  Electric  Telegraph..                                  .. -Thorn-Collins 1.00 


Partial  List  of  Titles  and  Authors    Continued 

PRICK 

Electric  Wiring  and  Lighting Knox-Shaad $1.00 

Estimating . Edward  Nichols ..   1.00 

Factory  Accounts Hathaway-Griffith 1.50 

Forging John  Lord  Bacon 1.00 

Foundry  Work Wm.  C.  Stimpson 1.00 

Freehand  and  Perspective  Drawing Everett-Lawrence 1.00 

The  Gasoline  Automobile . Lougheed-Hall . .' 2.00 

Gas  Engines  and  Producers Marks- Wyer 1.00 

Heating  and  Ventilation Charles  L.  Hubbard 1.50 

Highway  Construction _.Phillips-Byrne 1.00 

Hydraulic  Engineering Turneaure-Black 3.00 

Insurance  and  Real  Estate  Accounts Charles  A.  Sweetland  ...   1.50 

Knitting .... M.  A.  Metcalf 3.00 

Machine  Design Charles  L.  Griffin 1.50 

Machine-Shop  Work Frederick  W.  Turner 1.50 

Masonry  and  Reinforced  Concrete Webb-Gibson 3.00 

Masonry  Construction Phillips-Byrne 1.00 

Mechanical  Drawing Ervin  Kenison 1.00 

Modern  American  Homes H.  V.  von  Hoist 3.00 

Motion  Pictures David  S.  Hulfish 4.00 

The  Orders Bourne- von  Hoist-Brown  3.00 

Pattern  Making James  Ritchey 1.00 

Plumbing '_ Gray-Ball J 1.50 

Power  Stations  and  Transmission Geo.  C.  Shaad 1.00 

Practical  Aeronautics Chas.  B.  Hayward 3.50 

Practical  Bookkeeping James  B.  Griffith 1.50 

Practical  Lessons  in  Electricity Millikan-Knox-Crocker  _    1.50 

Reinforced  Concrete Webb-Gibson 1.00 

Railroad  Engineering Walter  Loring  Webb 3.00 

Refrigeration M.  W.  Arrowwood 1.00 

Sewers  and  Drains A.  Marston 1.00 

Sheet  Metal  Work William  Neubecker 3.00 

Stair-Building  and  Steel  Square Hodgson- Williams 1.00 

Steam  Boilers Newell-Dow 1.00 

Steam  Engines L.  V.  Ludy 1.00 

Steam  Turbines Walter  S.  Leland 1.00 

Steel  Construction E.  A.  Tucker 1.50 

Strength  of  Materials Edward  Rose  Maurer  ...   1.00 

Surveying Alfred  E.  Phillips 1.50 

Telephony Miller-McMeen 4.00 

Textile  Chemistry  and  Dyeing Louis  A.  Olney 3.00 

Textile  Design Fenwick  Umpleby 3.00 

Tool  Making Edward  R.  Markham  ___   1.50 

Valve  Gears  and  Indicators L.  V.  Ludy 1.00 

Water  Supply Frederick  E.  Turneaure. .   1.00 

Weaving H.  William  Nelson 3.00 

Wireless  Telegraphy  and  Telephony Ashley-Hay  ward 1.00 

Woolen  and  Worsted  Finishing John  F.  Timmerman 3.00 

Woolen  and  Worsted  Spinning Miles  Collins 3.00 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 

Los  Angeles 
This  book  is  DUE  on  the  last  date  stamped  below. 


?& 


MAY  151959., 

MAY  1  5 

8EP  1 3  1971 
SEP  7 


Form  L9-100m-9,'52(A3105)444 


bfumrhl 
Libr«y 

rr 
w 


A    000803865    5 
AUXILIARY 

SEP        73 


